Clarke ready for Warriors bow.
The creative centre, who joined from Northampton in the summer, is yet to play for Warriors after picking up an injury in pre-season.
As a result he has witnessed the previous two home games from the sidelines and watched in horror as both have ended in last-minute penalties denying his team victory. Olly Barkley-inspired Bath nicked a one-point win on opening day and a fortnight ago Freddie Burns snatched a draw when the Worcester front row was penalised for standing up. Worcester received subsequent apologies after it was found the referees had made a mistake in both instances.
So Clarke, who is due to start on the bench, is determined there is no repeat tomorrow evening. "It's not just any game, it's a home game. It's massive," he said.
"We were disappointed against Bath, we were the better team and didn't come away with the win we wanted.
"Against Gloucester we were the better team there and we came away with a draw, some people will see that as not too bad but the way we played it was a bad result for us in the end.
"You want to perform well at home, every home game is massive and Friday night back here at Sixways, we need the result. We have got to start getting the season going. A good win will get us a good bit of confidence, so London Irish is a good chance for us."
Irish picked up their first victory of the season against Bath last weekend, while Worcester are still looking for theirs and come into this match off the back of one of the most bizarre performances since they have been in the Premiership.
Against Northampton they were hammered out of sight for the first hour and were 37-3 down before they reeled off 28 unanswered points to steal two bonus points - and a first top-flight try bonus since 2008.
They still lost but they just about did enough to prevent major soulsearching just a few weeks into the season.
What has become clear, though, is that Worcester's discipline has not been good enough and Clarke sees that as something that has to be remedied.
"Generally we give away too many soft penalties," he said. "Giving teams that aren't performing well field position is a killer. You can play really well but if you keep giving away pens, teams will pin you back and you can't play.
"We just made a couple of simple mistakes off kick-off right at the end. Literally you catch the ball, set it up and the game is finished. It is just little things we have got to get going. We have got to keep working hard and keep learning."
Jon Clarke will be on bench