Celtic won narrowly to extend their lead at the top of the Scottish Premier League despite a below-par performance at home against St Mirren.
After a lacklustre first half the home side made three changes in an attempt to inject more cutting edge to their game in the second period.
It eventually paid off on 79 minutes when substitute Kris Commons fired in a low drive from 20 yards.
St Mirren's John Potter missed a good close-range chance in added time.
The win takes Celtic onto 73 points at the top of the SPL table, five ahead of Rangers, who are inactive until they travel to play their game in hand against Hamilton Accies on Sunday.
The hosts had come into the game off the back of a 3-1 midweek win over in-form Hibernian, but the performance in the opening 45 minutes was a far cry from that clinical display.
Manager Neil Lennon, serving the last game of his touchline ban, would have noted down just one real chance for his men.
That came after half-an-hour when Anthony Stokes rose to meet Cha Du-Ri's cross from the right-hand side, and the Irishman's header from seven yards went narrowly past the St Mirren post.
Other than that Celtic were sloppy in possession and struggled to get in behind a very well-organised Saints defence.
Beram Kayal, Celtic captain for the afternoon, and Ki Sung-Yeung in particular were guilty of wasteful passes.
And as the home crowd grew restless Ki and Charlie Mulgrew resorted to efforts from distance, which never troubled Paul Gallacher in the visitors' goal.
Instead, it was St Mirren, perhaps enjoying renewed confidence after winning their last two games, who looked more comfortable, and they had better chances to break the deadlock.
Michael Higdon watched a glancing header go across goal after 13 minutes, and then Steven Thompson had a glorious opportunity from Kenny McLean's cut-back.
But the Saints midfielder swung his foot and completely missed the ball from an excellent position just 10 yards from Fraser Forster's goal.
Shortly before the break, Celtic's James Forrest showed more urgency, taking the ball in from the right wing, and beating a couple of players before steering a shot past the far post.
But St Mirren had the last chance of the half, when Higdon was afforded acres of space at a corner, drifting away from his marker before badly scooping his shot over from around the penalty spot.
Shaun Maloney was given his first taste of action for more than four months after the break, with Gary Hooper making way having had a quiet game.
The home side began to show much more intent, putting St Mirren under some sustained pressure, but still they failed to really test Gallacher.
And although the league leaders made tracks down the wings, their crosses were often poor, and when Emilio Izaguirre burst through the middle from left-back his attempt to slip the ball through to Maloney was overhit and the move broke down like so many others.
With Ki and Ljungberg proving largely ineffectual, they were replaced by the more regular first XI pairing of Joe Ledley and Commons.
And the change paid off, as shortly afterwards Commons gave Celtic the goal which, until then, had looked unlikely for the hosts.
Maloney received the ball 18 yards out, dragged it across the box before laying it off to Commons who rattled a first-time shot low inside the post from around 20 yards.
As the game drew to a close, St Mirren's Potter was inches away from a spectacular equaliser with a rasping shot from 25 yards which flew just over the bar.
And the Saints defender had a wonderful chance to level in added time, but he lashed a left-foot volley wide from just seven yards after Celtic had failed to clear a corner.
Live text and stats
Saturday, 9 April 2011
11 Cha Du-Ri
07 Ljungberg (Commons 70)
18 Ki Sung-Yeung (Ledley 61)
33 Baram Kayal
88 Hooper (Maloney 46)
05 Mair (Barron 81)
14 McGregor yellow card
07 Murray (Wardlaw 81)
45 Mclean (Travner 72)
02 van Zanten,
33 Mooy ,
Ref: MurrayAtt: 50,318
Attempts on target
Attempts off target
92:59 The referee blows for the end of the match.
90:00+0:04 Effort on goal by John Potter from deep inside the penalty area misses to the right of the target.
89:37 Free kick awarded for a foul by Joe Ledley on Jim Goodwin. Jim Goodwin takes the free kick.
88:32 Foul by Marc McAusland on Anthony Stokes, free kick awarded. Direct effort from the free kick comes in from Anthony Stokes.
87:40 Gareth Wardlaw gives away a free kick for an unfair challenge on Beram Kayal. Direct free kick taken by Fraser Forster.
85:28 Corner taken by Jure Travner from the left by-line, Glenn Loovens makes a clearance.
85:01 Unfair challenge on David Barron by James Forrest results in a free kick. John Potter restarts play with the free kick.
84:33 James Forrest produces a left-footed shot from just outside the penalty box that goes wide left of the target.
83:58 Handball decision goes against Marc McAusland. Kris Commons takes the direct free kick.
82:57 Free kick taken by Fraser Forster.
82:57 Booking Darren McGregor is shown a yellow card for unsporting behaviour.
82:51 Darren McGregor concedes a free kick for a foul on Glenn Loovens.
80:34 Inswinging corner taken by Jure Travner.
80:34 Substitution Hugh Murray leaves the field to be replaced by Gareth Wardlaw.
80:34 Substitution David Barron on for Lee Mair.
79:57 Hugh Murray delivers the ball, clearance made by Charlie Mulgrew.
77:46 Assist by Shaun Maloney.
77:46 GOAL - Kris Commons:Celtic 1 - 0 St Mirren Kris Commons gets on the score sheet with a goal from just outside the area to the bottom left corner of the goal. Celtic
1-0 St Mirren.
76:16 Centre by Shaun Maloney, Paul Gallacher makes a save.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.