Tuilagi and Australia international Toomua have rarely featured together since Toomua arrived at the club last year, but they now appear for a Pool Four encounter that Leicester realistically must win to maintain quarter-final hopes.

A 33-10 defeat against Munster in Limerick last weekend left Tigers five points behind the Irish heavyweights, and they cannot afford to lose any further ground.

"Matt and Manu have been training hard, they are world-class operators and it’s great to have them back," Leicester head coach O’Connor said.

"We prepared well for last weekend, but we didn’t deliver on the day and were beaten by a very committed Munster side.

"Now we are looking at a big reaction at home this week. Pool Four is the tightest of all the groups in the competition, and all four teams still have everything to play for."

Saracens, thumped 46-14 at home by Clermont Auvergne in a weather-delayed game last Monday, face a return fixture in France on Sunday knowing they must win to keep pace with Pool Two leaders Clermont.

Saracens have lost their last six games in all competitions, and hopes of a third successive Champions Cup crown will be dented unless they triumph at Stade Marcel-Michelin.

"The players have been unbelievably positive, and they always surprise me with their ability and resilience to bounce back, to get on with a new job," Saracens defence coach Alex Sanderson told www.saracens.com.

"Obviously, we are gutted about results, but we’re an organisation that bases ourselves on performance and what motivates performance. That is how we support each other.

"It’s always easier preparing to play a team straight after you have already played them.

"With the environment we have here and the amount of work we do analysis-wise, we’ve had a good look at them, but more of an in-depth look at ourselves and what we need to do better because Clermont are good, but they are not 46 points better than us."

Elsewhere on Sunday, Pool Two strugglers Northampton begin life after sacked rugby director Jim Mallinder by tackling the Ospreys in Swansea, with Wasps needing victory over unbeaten Pool One leaders La Rochelle at the Ricoh Arena to remain in quarter-final contention.

Wasps welcome back Nathan Hughes after injury, and Wasps rugby director Dai Young said: "We have worked hard on our analysis of last Sunday’s game (La Rochelle beat Young’s team 49-29), and now need to make sure we apply lessons learnt.

"They have got quality players who will create problems, but we’ve also shown that if we get reasonable possession we can take the game to them and score tries."