Substitute Peter Ambrose scored a late goal as rampant Aberdeen eked out a 1-0 win over Dundee United to move three points clear at the top of the Scottish Premiership. Jimmy Thelin’s side looked set to be frustrated by their stubborn visitors on a tense evening at a packed Pittodrie. But Nigerian forward Ambrose sparked jubilant scenes as he notched the only goal of the game in the 84th minute, just two minutes after entering the fray. The victory maintained the Dons’ stunning 15-game unbeaten run under Jimmy Thelin, 14 of which have been wins, and ensured they stole a march on Celtic, who visit Motherwell on Sunday. They are now nine points clear of third-place Rangers, who head to Pittodrie on Wednesday. There were three changes to the Dons side that started the 2-2 draw at Celtic Park the previous weekend as Ante Palaversa, Duk and Esther Sokler replaced Graeme Shinnie, Leighton Clarkson and the injured Kevin Nisbet. United manager Jim Goodwin, a former Aberdeen manager, made one alteration to the side that kicked off the dramatic 3-2 victory over Hibernian as Kristijan Trapanovski came in for Miller Thomson. There was a sense of anticipation among the home support before kick-off in the Granite City, but the Dons were largely stifled early on by a well-organised United side, happy to drop deep in numbers, close off space and hit on the counterattack. The hosts’ first notable opportunity came in the 24th minute when Topi Keskinen latched on to a long diagonal pass from Jack MacKenzie and looked to be clean through but Kevin Holt got back to make a vital tackle on the edge of the box before the Finn could pull the trigger. Despite enjoying the majority of the possession, the Dons’ only attempt of the first half came in the 33rd minute when Palaversa rifled a low shot just wide from 25 yards out after Declan Gallagher cleared a MacKenzie cross into his path. United looked dangerous on the sporadic occasions they ventured forward and Sam Dalby and Luca Stephenson both headed over the bar before the interval. Having seen his side fail to score in the first half of a home league game for the first time this season, Thelin sent on Shayden Morris for Keskinen at the start of the second period and within a minute of the restart the substitute burst down the right and fizzed a low delivery across the six-yard box that found no takers. Aberdeen threatened again when MacKenzie surged into the box and cut the ball back for Jamie McGrath, whose low shot was diverted behind by Jack Walton. The United keeper made another big save when he pushed Morris’s angled shot wide after the winger had played an incisive one-two with Sokler to get himself free in the box. Aberdeen thought they had gone ahead in the 70th minute when Sokler headed a Morris cross towards goal but Walton dived superbly down to his right to claw it out. Just as it looked like the Dons were going to be frustrated, however, Ambrose forced the ball in from six yards out after Gavin Molloy’s cross had been knocked back into the danger area by Nicky Devlin at the back post. St Johnstone produced the perfect comeback to secure their second Premiership win in a row - 2-1 against Dundee at Dens Park. The Dark Blues took the lead in the first half through skipper Simon Murray, with Saints substitute Graham Carey drawing his side level after the break. But St Johnstone snatched all three points thanks to a dramatic last-minute goal from captain Nicky Clark. Liam Donnelly’s sending off turned the game in Ross County’s favour as they defeated Kilmarnock 2-1 to move one point above the Ayrshire team in the Scottish Premiership table. It had looked like the visitors were in control in Dingwall after taking the lead in the 39th minute through Corrie Ndaba. A second yellow card for Donnelly on the hour mark changed the game completely though, with Jordan White’s goal immediately afterwards and an own goal from Joe Wright in the 82nd minute ensuring the points remained in the Highlands.