Director of rugby Les Kiss admits the next two weekends are make or break time for Ulster in terms of the European Champions Cup.
The Irish Province travel to The Stoop for Sunday afternoon’s (kick-off 1pm) Pool One game against Aviva Premiership side Harlequins.
It is the traditional back to back games in the competition and rounds three and four always throw up some significant results.
It can also open or close a door for some sides’ campaigns in Europe even with two more rounds to come.
Ulster currently lie third in Pool One, six points behind leaders La Rochelle and a point behind Wasps.
Harlequins know their challenge will be over if Kiss’s side can produce the goods on the road.
Ulster are unbeaten in their last Guinness PRO14 games with two wins and a draw - but those have been against average opposition and Harlequins - fresh from a win last weekend against reigning back to back European Champions Saracens will prove a much sterner examination of the Irish Province.
Ulster do have several players returning from international duty and injuries, but yesterday morning were dealt another blow when captain and hooker Rory Best was ruled out with a foot infection.
One player does not make a difference but Best, who is also the Irish captain, is a talismanic figure in the side and boasts a wealth of experience in huge games like these.
Rob Herring, making his return from Ireland duty, will start in the front row with John Andrew being promoted to the bench.
Disappointed not be going to England with their captain available to play Kiss said: “What happened to Rory is unfortunate, but we have Rob Herring who has done a good job all year.
“He had a great Test match for Ireland recently, brings a lot of experience and then John Andrew steps up who is really growing as a back up number two and really fighting hard to get into that starting team.”
Ulster are boosted by the return of internationals Iain Henderson, who will skipper the side again, and Jacob Stockdale on the wing.
The former Wallace High School player has been the talk of the country in recent weeks after his performances in the green jersey against South Africa and Argentina during the November Guinness Test series.
In terms of the importance of the games given the current situation in Europe, Kiss admitted the next two games determined much.
“You look through the pools and these home and away games for all the teams and it is make or break.
“Some teams have a breathing space. It is big for Europe and it is important to understand what it means.
“If you can nail the first one you can put scoreboard pressure across all the pools. It is interesting what happens there and this happens here for us.
“We get the money we come home we have changed the nature of the competition from what everyone thinks they have to do and then we get the comforts of home - it will not be easy,” he added.
Harlequins: Mike Brown (c); Charlie Walker, Alofa Alofa, Jamie Roberts, Tim Visser; Marcus Smith, Danny Care; Joe Marler, Elia Elia, Kyle Sinckler, George Merrick, Charlie Matthews, Renaldo Bothma, Chris Robshaw, Mat Luamanu
Replacements: Dave Ward, Lewis Boyce, Phil Swainston, Dino Lamb, Archie White, Ian Prior, Winston Stanley, Ross Chisholm
Ulster: Charles Piutau; Craig Gilroy, Tommy Bowe, Stuart McCloskey, Jacob Stockdale; Christian Lealiifano, John Cooney; Callum Black, Rob Herring, Wiehahn Herbst, Alan O’Connor, Kieran Treadwell, Iain Henderson (c), Sean Reidy, Nick Timoney
Replacements: John Andrew, Andy Warwick, Ross Kane, Matt Rea, Chris Henry, Paul Marshall, Peter Nelson, Louis Ludik