The draw with Munster in Belfast appears to have made up Neil Doak's mind. Sure, that sharp cut-out pass by Paddy Jackson and touchline conversion to snatch a result from what seemed certain defeat didn't salvage a home semi-final, but its value is still unquantifiable.
Throughout Jackson's gruelling, confidence-dipping, injury-cursed season, Joe Schmidt kept mentioning his name when answering questions about Ian Keatley, Ian Madigan and Johnny Sexton.
Now we see why. Jackson makes way for Ian Humphreys this afternoon because Ulster and Doak are not putting much stock in victory here. For one, Glasgow are the most consistent Pro 12 side over the past two years.
Gregor Townsend’s team at home are like Leinster were until recently: almost irresistible; machine-like.
Win on the road
And, anyway, Munster and Ospreys should also win in Cork and Galway, so that will sort that out. Ulster will need to win on the road – at Thomond Park, the Liberty stadium or back in Scotstoun – if they want to play for the title at Ravenhill on May 30th.
So, some bodies are resting up. Callum Black (hamstring), Wiehahn Herbst (toe), Darren Cave (shoulder), Jared Payne (ankle), Dan Tuohy (hip), Peter Nelson (hamstring) and Craig Gilroy (hamstring) are on ice, with Payne and Tuohy almost certain to return for the play-offs.
The non-suspension of Iain Henderson, an all-Welsh disciplinary committee concluding Nigel Owens's red card for clearing Ronan O'Mahony was erroneous, sees him retained in the match day squad.
Still, Ulster are keeping their powder dry, as Henderson is joined on the bench by Rory Best, Roger Wilson (having recovered from concussion), Ruan Pienaar, Tommy Bowe and Jackson.
Glasgow have gone the other way. After losing to the Ospreys last week, Sean Lamont returns to the left wing, so Niko Matawalu goes to scrumhalf instead of Henry Pyrgos. Finn Russell replaces Duncan Weir at outhalf to strengthen a backline still without Mark Bennett and Sean Maitland
Also, Ali Kellock returns to the pack in what could be his last game in Glasgow.
“Playing in front of around 10,000 supporters at home for only the second time in our history is sure to be a great experience for our players,” said Townsend. “We will be doing all we can to reward our supporters with a home semi-final the following week.”
Glasgow feel more like Leinster circa 2008 but they are the growing force around the league. Ulster can outfox them with a full deck in the semis, but not here.
GLASGOW WARRIORS: S Hogg; T Seymour, R Vernon, P Horne, S Lamont; F Russell, N Matawalu; R Grant, D Hall, R de Klerk; J Gray, A Kellock (capt); J Strauss, C Fusaro, A Ashe.
Replacements: P MacArthur, G Reid, M Cusack, L Nakarawa, R Wilson, H Pyrgos, D Weir, P Murchie.
ULSTER: L Ludik; R Scholes, S Arnold, S McCloskey, M Allen; I Humphreys, P Marshall; A Warwick, R Herring, R Lutton; L Stevenson, F van der Merwe; C Ross, C Henry (capt), R Diack.
Replacements: R Best, K McCall, B Ross, I Henderson, R Wilson, R Pienaar, P Jackson, T Bowe.
Referee: I Davies (WRU).
Previous meetings: October 2014: Ulster 29-9 Glasgow; April 2014: Glasgow 27-9 Ulster; September 2013: Ulster 12-13 Glasgow.
Verdict: Glasgow win.