West Brom kept their survival hopes alive and dented Manchester United's bid to finish second in the Premiership with a battling draw at Old Trafford.
Ryan Giggs put United ahead with a free-kick after 20 minutes, fired past injured keeper Russell Hoult.
Hoult, who suffered a groin injury, was replaced by Tomasz Kuszczak, who made a string of outstanding saves.
The Baggies levelled after 61 minutes from Rob Earnshaw's penalty after John O'Shea fouled Geoff Horsfield.
United boss Sir Alex Ferguson rested Roy Keane, Ruud van Nisterlrooy, Wayne Rooney and Paul Scholes from his starting line-up, giving rare opportunities to Alan Smith and Kleberson.
And they had no trouble making an impact as United exterted total domination in the first 45 minutes.
West Brom suffered a setback when goalkeeper Hoult appeared to suffer a groin injury - and they paid a heavy price as United took the lead after 19 minutes.
Giggs took a quick free-kick after Thomas Gaardsoe fouled Smith, and Hoult's lack of mobility meant he could only scramble across his line in vain.
Hoult was replace by Kusczak, who distinguished himself with three fine saves before half-time.
He did well to block Quinton Fortune's header, then twice denied Cristiano Ronaldo as United mounted wave after wave of attacks.
Rio Ferdinand wasted a glorious opportunity to double United's lead two minutes before the interval, when he completely mis-kicked in front of goal.
It was an incident that led to widespread ironic jeers and chanting from United fans angry at Ferdinand's delay in signing a new contract at Old Trafford.
The pattern did not alter after the break, with Kuszczak saving well from Kleberson.
And after 52 minutes the Brazilian blazed over from 10 yards when unmarked after good work from Fortune.
West Brom upped the tempo, and it needed a brave block from Roy Carroll to stop Kevin Campbell as he closed in on a half-chance.
Ronaldo was doing everything but score, and he was inches wide when he raced on to a superb long pass from Phil Neville.
Albion had barely been seen as an attacking force, but they were level after 61 minutes, courtesy of a controversial penalty from Earnshaw.
Referee Mark Halsey pointed to the spot as O'Shea tangled with Horsfield, and despite furious protests Earnshaw scored easily.
The setback prompted a triple change by Ferguson, who sent on Rooney, Scholes and Louis Saha for Smith, Kleberson and Neville.
United laid siege to the West Brom goal, with Scholes hitting the post from a free-kick and Kuszczak again outstanding to deny Rooney from long-range.
Manchester United manager Sir Alex Ferguson:
"It was a terrible result considering the chances we had.
"It was ridiculous but that's happened so many times. It was a terrible giveaway and it's a pity because I think we could have got second place.
"It's very difficult now. It's frustrating, if you look at our record this season it's been about giving points away to the bottom teams."
West Brom boss Bryan Robson:
"It's a good result for us. At least now if we win our last game a draw is not good enough for the others.
"We got a few breaks but I think the players deserved that on their second-half performance.
"If we do stay up it will probably be the best achievement I've had in football."
Man Utd: Carroll, Brown, Ferdinand, Silvestre, O'Shea, Ronaldo, Phil Neville (Scholes 67), Kleberson (Rooney 67), Fortune, Giggs, Smith (Saha 67).
Subs Not Used: Howard, Miller.
Goals: Giggs 20.
West Brom: Hoult (Kuszczak 22), Albrechtsen, Gaardsoe, Clement, Robinson, Gera (Inamoto 83), Wallwork, Greening, Earnshaw, Campbell, Horsfield (Kanu 66).
Subs Not Used: Scimeca, Moore.
Goals: Earnshaw 60 pen.
Ref: M Halsey (Lancashire).