WORCESTER Warriors have no margin for error in tonight’s European Challenge Cup derby against Gloucester at Sixways, admits fly-half Ryan Lamb.

The hosts could be struggling to qualify for the knockout stages if they lose to holders Gloucester, who top Pool Four with two victories.

Warriors won their group opener 19-3 against French club La Rochelle but then lost 27-8 in Italy against Zebre.

Only the five pool winners and three best-placed runners-up will progress to the quarter-finals.

New England head coach Eddie Jones will be at tonight’s game.

Former Gloucester player Lamb said: “If we have any ambition in this competition, we have got to win tonight.

“Gloucester have had two wins from their first two matches so they are the team in the group everyone wants to chase down. The double-header with Gloucester over the next week is key for us.

“If we are to proceed in this competition, we have to take the opportunity at Sixways. It’s nice to get a runout against a top-quality side.”

Gloucester have taken an early grip on the pool after winning 23-10 at home to Zebre and 33-20 at La Rochelle.

Warriors’ return European fixture is at Kingsholm next Thursday (7.45pm).

The Cherry and Whites edged Warriors 24-22 in a hard-fought Premiership derby at Kingsholm in October.

Lamb said: “We know it’s going to be a tough challenge but we’re back at home and have played well at Sixways.

“We’ve only lost once at home this season against Leicester Tigers (29-20), which was a game we perhaps should have won.”

Lamb was born and bred in Gloucester and played 58 times for his home city club between 2004 and 2009. He now lives between Cheltenham and Gloucester.

“I always look forward to playing against Gloucester because they are a good side and, being my hometown, it’s a place I’ve had a lot of good years at,” he said.

“My father, mother, brother and sister still live in Gloucester so the city is a big part of our lives. I still follow the rugby club and so do my family. Gloucester have a lot of strength in depth, particularly in the front five and the forward pack, so it will be a big challenge.”

Warriors paid the price for a pedestrian start in their surprise defeat at Zebre.

Lamb said: “We went to Zebre with a very inexperienced side, especially in the forward pack, and our set-piece struggled. They had an international front row and it was a tough test.

“It was a learning curve and good for the lads to play against some international-class forwards. But we dug ourselves a hole in the first half and it was hard to get back into the match.”

Lamb is keen to reaffirm his partnership with scrum-half Charlie Mulchrone, who captains Warriors tonight.

“He is a leader, very vocal on the pitch and a good motivator and I am sure the boys will be good for him,” he said.

“Charlie is an attacking nine who likes to attack on the fringes so hopefully we will gel, although we haven’t played too much together.

“We had a few games against London Scottish and Cornish Pirates last season so hopefully we can repeat the form we showed then.”