Reigning champions Leinster were toppled by beaten finalists Glasgow Warriors at Scostoun, with Stuart Hogg slotting over the winning penalty with the last kick of the game.
Warriors stormed to a 19-0 lead with tries from Peter Horne, Josh Strauss and Jonny Gray, but then Leinster staged a late revival.
Jack McGrath and Tom Denton found their way over the whitewash to put the Irish province into the lead for the first time, but ill-discipline in the dying minutes led to Hogg’s successful penalty.
Peter Horne will make his first Scotland start in Saturday’s Test against Canada in Toronto.
The Glasgow centre replaces the injured Duncan Taylor in one of four changes to the side that beat USA 24-6.
Grant Gilchrist takes Jim Hamilton’s place in the second row, while prop Moray Low is in for Geoff Cross.
Kelly Brown returns to the back row for his 64th cap, with scrum-half Greig Laidlaw retaining the captaincy and Finn Russell staying at fly-half.
Russell, 21, enjoyed a promising debut in Texas along with Glasgow team-mate Gordon Reid, who also keeps his place in the front row. Brown’s inclusion means Blair Cowan drops to the bench after winning his first cap.
Peter Horne can’t wait to get back on the field for his first start for Glasgow in nearly a year.
The centre suffered knee ligament damage playing for Scotland last June, but is fit again and starts in the huge PRO12 clash with Ulster at Scotstoun this evening.
Glasgow Warriors scrum-half Niko Matawalu will miss the start of the season after the Fiji international broke a bone in his foot. The 24-year-old has damaged the fifth metatarsal in his right foot during training and has undergone surgery.
Rob Harley has been called into the Scotland squad as injury cover after fellow forward Jim Hamilton returned home to be with his expectant wife.
Scotland will field three new caps in their team for Saturday’s international against Samoa in Durban, the first of their three games in the Castle Lager Incoming Series. The debutants are 24-year-old Edinburgh Rugby full-back Greig Tonks and the Glasgow Warriors duo, centre Alex Dunbar, 23 and hooker Pat MacArthur, 26.
Ten uncapped players have been named in interim head coach Scott Johnson’s first Scotland squad. The 35-strong squad will convene in Glasgow next Sunday for a three-day training camp ahead of the RBS 6 Nations Championship.
Head coach Andy Robinson has today named seven uncapped players in his 34-strong Scotland squad for training at St Andrews next week in preparation for the first EMC Test against New Zealand at Murrayfield next month.