Celtic struggled without a clutch of key stars but Alan Thompson's first-half penalty edged the injury-hit champions just four wins away from retaining the Premier League title.

But the bad blood between the two sides resurfaced again late on when the Englishman and Aberdeen substitute Hicham Zerouali were sent off after an off-the-ball clash.

But Celtic manager Martin O'Neill found himself down to the bare bones with John Hartson suspended, Henrik Larsson, Chris Sutton, Bobo Balde, Joos Valgaeren injured and Olivier Tebily absent.

The Irishman, who celebrated his 50th birthday yesterday, drafted in veteran skipper Tom Boyd while young duo Stephen Crainey and Shaun Maloney also came into a new-look side.

But it was unsung hero Thompson who showed the composure needed to move his side a massive 16 points clear of nearest challengers Rangers, who play tomorrow.

Despite the changes the home side started brightly with veteran Lubo Moravcik taking the initiative early on.

Aberdeen defender Russell Anderson needlessly gave the ball away to Lubo Moravcik in the very first minute, but he failed to find the power and direction to beat Peter Kjaer from 22 yards.

The mercurial Slovakian again found himself in a good position moments later when he brilliantly controlled Neil Lennon's long ball before firing a fierce right-foot shot just past the post.

Celtic seemed eager to grab a quick goal in front of the watching Scotland coach Berti Vogts and they carved out a good chance in the ninth minute following a good three-man move.

Moravcik found the over-lapping Didier Agathe and his cross was headed over by Johan Mjallby from 10 yards.

But from then on they were finding it difficult to create any real gilt-edged chances and seemed desperately short of ideas.

Young striker Maloney tried to catch Kjaer off guard with a long-range drive in the 15th minute from Thompson's pass, but he pulled his effort well wide.

The home side did have the ball in the net two minutes later when Moravcik threaded the ball through to Stilian Petrov who chipped onrushing Kjaer, but the linesman flagged for offside.

Referee John Underhill's first involvement in the game came in the 20th minute when he gave Darren Young, who crocked Sutton in midweek, a ticking-off after fouling Moravcik.

But the Aberdeen man was not so lucky five minutes later when he was booked for a clash with Lennon to give Celtic a free-kick and Moravcik curled a 15-yard effort well wide of the bar.

Despite all Celtic's efforts and probing going forward it was Aberdeen who created the best chance of the first-half with their first real attack on goal on the half-hour.

Roberto Bisconti found Robbie Winters in the box and after cutting inside Boyd he had all the goal to aim for, but he shot straight at a relieved Robert Douglas in the Celtic goal.

The home side continued to be restricted to half-chances and Paul Lambert chipped just wide of the goal moments later after exchanging passes with Crainey just outside the box.

Aberdeen again went close with the Celtic defence caught napping in the 32nd minute when Anderson rose in the box to meet Winters' corner, but he headed wide of the mark.

But in the final seconds of the half Celtic took the lead.

Eugene Dadi was adjudged to have held Crainey down in the box and Thompson fired low into the bottom corner from the spot.

But the midfielder could have killed off Aberdeen's hopes within 30 seconds of the restart when Agathe found him at the far post with a wonderful cross, but he side-footed over the bar.

Kjaer almost made a hash of Thompson's inswinging corner in the 51st minute, but his touch took the ball away from the head of Mjallby who would have surely scored.

O'Neill brought on another youngster in the 58th minute when he replaced the old legs of Moravcik with Jamie Smith while Hicham Zerouali came on for Dadi as the visitors chased an equaliser.

But just minutes later Kevin McNaughton needed to head behind Agathe's dangerous cross with Thompson lurking before Kjaer saved Mjallby's cheeky backheel from the Englishman's cross.

The home fans began to get restless and anxious the longer the match went on without another goal.

But Smith came within inches of settling the nerves when his right-foot volley clipped the post from Agathe's cross.

Bisconti became the second man booked in the 75th minute for persistent fouling before Kjaer comfortably saved Thompson's powerful 25-yard free-kick.

Moments later Celtic went close again when Agathe found Smith, but his cross was just too far ahead of Maloney.

But the bad feelings between the two sides resurfaced in the 79th minute when Thompson and Zerouali were sent off.

The Englishman pushed the Moroccan after Lambert was booked for fouling Darren Mackie and the Aberdeen man took a swing at him and Underhill brandished red cards.

The rowing pair needed to be separated as they left the field, but it is sure to steal the headlines again with four players now being sent off in the last three games between the teams.

Another suspension will not be welcomed by O'Neill but it is a good job that they are now just four wins away from glory.

Teams:

Celtic Douglas, Boyd, Mjallby, Crainey, Agathe, Lambert (McNamara 82), Lennon, Petrov, Thompson, Moravcik (Smith 58), Maloney.

Subs Not Used: Gould, Sylla, Guppy.

Sent Off: Thompson (79).

Booked: Lambert.

Goals: Thompson 45 pen.

Aberdeen Kjaer, McNaughton, McGuire, Whyte, McAllister, Anderson, Darren Young, Winters, Bisconti, Mackie, Dadi (Zerouali 58).

Subs Not Used: Preece, Clark, Tiernan, O'Donoghue.

Sent Off: Zerouali (79).

Booked: Darren Young, Bisconti.

Att: 59,564

Ref: J Underhill (Scotland).