La Rochelle comfortably lead the chase for the knockout stages next year, and Ulster can consolidate second place with a win before welcoming the French team to Belfast in January and then a mission to complete a double over Wasps in Coventry.
Tonight, Tommy Bowe, deployed at centre in the 17-5 win in London on Sunday, misses out with a hamstring strain, and Louis Ludik has been drafted in to partner Stuart McCloskey in midfield, as Irish international wings Jacob Stockdale and Craig Gilroy complete a threatening back three with All Black Charles Piutau.
Chris Henry came off the bench at The Stoop and the flanker impressed enough to earn a starting place, with Sean Reidy now named as a replacement.
The visitors are without flanker Chris Robshaw and scrum-half Danny Care, due to concussion, and England prop Joe Marler is also ruled out through injury. Another England international, combative full-back Mike Brown, is a replacement, as is Scotland wing Tim Visser.
Harlequins director of rugby John Kingston admitted the club’s European ambitions had ended at the weekend and that his priority is now the Premiership, which coloured his Belfast selection.
“We’re very disappointed at losing on Sunday and we accept we are out of Champions Cup contention. That said, we are looking forward to playing Ulster and I’m demanding a positive performance ahead of our return to the Aviva Premiership.”
Ulster head coach Jono Gibbes anticipated Quins making changes, but always intended to limit his own tweaks.
“With a just a five-day turnaround, it’s a balance of rewarding guys for Sunday’s performance and freshening up a few things.
“When it mattered, we got good scrum stability, we stopped their drive and we got on the front foot and we managed the last 20 minutes better than we have in some recent league matches,” said Gibbes, who still believes there is room for improvement in all departments.
“The nature of Europe is that the back-to-back games just before Christmas sort out a lot of things, but we’re not too worried about the quarter-final ramifications.”
Gibbes said his players had managed the snowstorm conditions at The Stoop better than Harlequins, but he’d like tonight’s game to be played in better weather.
“We want to make it a bad night for them, fair enough, so we have to make it an uncomfortable evening for Quins.”