But an expectant home crowd, buoyed by a moving tribute to legendary former skipper Bobby Moore and the work carried out by the
cancer fund set up in his memory,
could hardly have enjoyed a better start to their afternoon.
A half-cleared corner was headed back into the danger area by Thomas Hitzlsperger and Keane, showing great awareness to stay onside, swivelled neatly and crashed the ball past Brad Friedel.
And the Hammers seemed intent on building on their perfect start.
Manager Avram Grant's decision to play Carlton Cole, Victor Obinna and Keane in a three-pronged attack caused problems from the start.
Cole was the main goalscoring threat and saw a shot blocked after being slipped in by Keane and then from Gary O'Neil's searching long ball he forced Friedel into a superb sprawling stop.
Cole also had a shout for a penalty waved away and the hosts barely had time to lament the absence of their midfield mainstay Scott Parker, who was missing with his Achilles injury.
But Manuel da Costa was forced off through injury and Villa began to settle after after their poor start.
Stiliyan Petrov congratulates Darren Bent after his equaliser
The pace of Ashley Young and power and knowhow of Emile Heskey were now proving every bit as threatening as Keane's guile and Cole's direct running.
Ashley Young wriggled inside from the left flank but his shot deflected wide and the winger also tested Robert Green from 20 yards.
Bent then headed home from Stewart Downing's fine right-wing cross but the goal was harshly disallowed for a push on Lars Jacobsen.
However, Bent did not have to wait long and, as good as the finish was by the England striker, Hammers manager Grant will have been furious with the defensive disaster that allowed him the chance.
Mark Noble dallied on the ball in his penalty box allowing Heskey to win possession and when the ball was cleverly worked into the box via Luke Young, Bent glanced his header past Green.
The visitors grew in confidence and began the second half in blistering fashion with Bent and Ashley Young once again the main threats.
Bent's persistence created a chance but Green made a decent block at his near post and then Cole hacked away from his own line when James Collins headed towards goal.
The pressure was relentless. Ashley Young curling's free-kick was superbly tipped away by Green and Villa's top scorer Bent also curled an 18-yard strike just wide via a deflection.
West Ham were becoming increasingly disjointed and with their confidence looking brittle after two heavy defeats in their last two outings, Villa sensed the victory was theirs for the taking.
Grant sets 41-point target
Kyle Walker's fine run teed up another chance for Bent but the striker somehow fluffed his kick from close range and Ashley Young then drifted a shot agonisingly wide.
West Ham's only noteworthy chance of the second half came in the final four minutes when Cole was unable to loop a tricky bouncing ball over Friedel.
And moments later the visitors were celebrating maximum points when Ashley Young retrieved the ball on the right wing and his delightful cross was gleefully headed home from point-blank range by Agbonlahor.
For Villa, it was only the second time they have won back-to-back matches this season, while the Hammers have slipped to a third consecutive defeat.
90:00+4:52 The referee blows for the end of the match.
90:00+1:58 Stewart Downing takes a shot. Robert Green makes a save.
90:00+0:44 The assist for the goal came from Ashley Young.
90:00+0:44 GOAL - Gabriel Agbonlahor:West Ham 1 - 2 Aston Villa Gabriel Agbonlahor grabs a headed goal from close in. West Ham 1-2 Aston Villa.
87:03 Free kick awarded for a foul by James Collins on Carlton Cole. Demba Ba has a direct shot on goal from the free kick, save
made by Kyle Walker.
86:19 Corner taken by Thomas Hitzlsperger.
85:30 Effort on goal by Carlton Cole from inside the box misses to the right of the target.
85:09 Nigel Reo-Coker takes a shot. Robert Green makes a save.
83:46 Corner taken left-footed by Stewart Downing from the right by-line, Carlton Cole manages to make a clearance.
82:17 Thomas Hitzlsperger produces a left-footed shot from just outside the box that misses to the right of the goal.
78:42 Foul by Zavon Hines on Luke Young, free kick awarded. Richard Dunne takes the direct free kick.
78:12 Header by Darren Bent from deep inside the penalty area misses to the left of the target.
77:45 Inswinging corner taken from the left by-line by Ashley Young, Matthew Upson manages to make a clearance.
76:36 Substitution Emile Heskey leaves the field to be replaced by Gabriel Agbonlahor.
76:36 Zavon Hines takes a shot. Blocked by Richard Dunne. Effort on goal by Thomas Hitzlsperger from just outside the area goes
harmlessly over the target.
76:10 Ashley Young produces a right-footed shot from the edge of the box and misses to the right of the goal.
75:07 Inswinging corner taken right-footed by Ashley Young, save made by Robert Green.
74:40 The assistant referee flags for offside against Carlton Cole. Free kick taken by James Collins.
Correction - 72:42 Darren Bent takes a shot. Clearance made by Daniel Gabbidon.
72:42 Darren Bent takes a shot. Daniel Gabbidon makes a clearance.
72:11 Free kick awarded for a foul by Zavon Hines on Richard Dunne. Richard Dunne takes the free kick.
69:31 The assistant referee signals for offside against Demba Ba. Free kick taken by Brad Friedel.
68:54 Ashley Young produces a right-footed shot from the edge of the box and misses to the right of the target.
66:04 Foul by Daniel Gabbidon on Emile Heskey, free kick awarded. James Collins takes the free kick.
62:45 The referee blows for offside. Indirect free kick taken by Matthew Upson.
61:43 Substitution Demba Ba on for Gary O'Neil.
57:08 Richard Dunne takes the free kick.
57:08 Substitution Victor Obinna goes off and Zavon Hines comes on.
57:08 Gary O'Neil challenges Luke Young unfairly and gives away a free kick.
56:08 Ashley Young takes a shot. Lars Jacobsen gets a block in. Corner from left by-line taken by Ashley Young.
54:01 Darren Bent takes a shot. Blocked by Matthew Upson. Outswinging corner taken from the right by-line by Ashley Young, Headed
effort from inside the area by Richard Dunne misses to the left of the target.
52:13 Free kick awarded for an unfair challenge on Ashley Young by Victor Obinna. Stewart Downing crosses the ball in from the free
kick, clearance by Daniel Gabbidon.
51:17 Matthew Upson challenges Stewart Downing unfairly and gives away a free kick. Ashley Young restarts play with the free kick.
50:25 Corner taken by Ashley Young.
47:20 Mark Noble concedes a free kick for a foul on Ashley Young. Ashley Young has a direct shot on goal from the free kick, Robert
Green makes a save. Inswinging corner taken left-footed by Stewart Downing from the right by-line, clearance made by Lars
Jacobsen. Corner from the right by-line taken by Ashley Young, clearance made by Daniel Gabbidon.
45:53 Darren Bent takes a shot. Save by Robert Green. Corner from the left by-line taken by Ashley Young, James Collins takes a
shot. Clearance by Carlton Cole.
45:01 The second half kicks off.
45:00+1:17 The players leave the pitch at half time.
44:17 Gary O'Neil has an effort at goal from just outside the area which goes wide of the left-hand post.
43:41 Corner from the right by-line taken by Thomas Hitzlsperger, save by Brad Friedel.
42:21 Carlton Cole is ruled offside. James Collins restarts play with the free kick.
41:13 The referee blows for offside. Brad Friedel takes the indirect free kick.
40:26 Unfair challenge on Mark Noble by Ashley Young results in a free kick. Robert Green takes the free kick.
35:59 Assist on the goal came from Luke Young.
35:59 GOAL - Darren Bent:West Ham 1 - 1 Aston Villa Darren Bent finds the net with a headed goal from inside the six-yard box. West Ham 1-1 Aston Villa.
34:10 Effort on goal by Ashley Young from just inside the penalty box goes harmlessly over the target.
33:46 Thomas Hitzlsperger has an effort at goal. Save by Brad Friedel.
Correction - 26:51 Darren Bent takes a shot. Blocked by Victor Obinna. Inswinging corner taken from the left by-line by Ashley Young, Headed
effort from deep inside the penalty area by James Collins goes harmlessly over the crossbar.
26:51 Darren Bent takes a shot. Blocked by Victor Obinna. Inswinging corner taken by Ashley Young from the left by-line, Headed
effort from deep inside the penalty area by Darren Bent goes harmlessly over the crossbar.
25:03 Victor Obinna takes a shot from 20 yards. Save made by Brad Friedel.
23:11 Darren Bent gives away a free kick for an unfair challenge on Lars Jacobsen. Robert Green takes the direct free kick.
20:29 Carlton Cole takes a shot. Brad Friedel makes a save. Corner taken left-footed by Thomas Hitzlsperger, save made by Brad Friedel.
Correction - 19:31 Ashley Young takes a shot. Comfortable save by Robert Green.
19:31 Ashley Young takes a shot. Save made by Robert Green.
18:09 The referee blows for offside against Carlton Cole. Brad Friedel takes the free kick.
13:30 Indirect free kick taken by Robert Green.
13:30 Substitution Manuel da Costa goes off and Daniel Gabbidon comes on.
13:30 The offside flag is raised against Darren Bent.
9:09 Robbie Keane takes a shot. Blocked by Richard Dunne.
7:04 Ashley Young takes a shot. Blocked by Matthew Upson. Ashley Young takes the inswinging corner, Headed effort on goal by Richard
Dunne from inside the penalty box misses to the right of the target.
6:00 Nigel Reo-Coker fouled by Thomas Hitzlsperger, the ref awards a free kick. Nigel Reo-Coker takes the direct free kick.
Correction - 5:07 Carlton Cole takes a shot. Luke Young gets a block in. Corner taken right-footed by Mark Noble, Stiliyan Petrov makes a clearance.
5:07 Carlton Cole takes a shot. Luke Young gets a block in. Inswinging corner taken by Mark Noble, Stiliyan Petrov makes a clearance.
4:17 The assistant referee flags for offside against Darren Bent. Robert Green restarts play with the free kick.
1:45 Thomas Hitzlsperger provided the assist for the goal.
1:45 GOAL - Robbie Keane:West Ham 1 - 0 Aston Villa Goal scored by Robbie Keane from close range to the top left corner of the goal. West Ham 1-0 Aston Villa.
1:12 Inswinging corner taken right-footed by Mark Noble from the left by-line, clearance made by Richard Dunne.
0:13 Stiliyan Petrov has an effort at goal from just outside the area which goes wide of the left-hand post.
0:00 The ref blows the whistle to begin the match.
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