Bristol Bears will face opponents with an "unbelievable" track record when they host four-time winners Leinster in their Investec Champions Cup opener on Sunday, director of rugby Pat Lam has said.

Leo Cullen's side will arrive at Ashton Gate with a perfect record from seven United Rugby Championship (URC) games, but Lam believes the joint-Premiership leaders with Bath can hold their own in Europe.

"This is probably the best prepared we [could be] in terms of form and where we're at," said Lam, who triumphed in the competition as a Northampton Saints player in 2000.

"The Champions Cup is somewhere we aspire to be, and to be here and play Leinster, with their unbelievable history, is the type of rugby we want to be involved in. This is as good as it gets."

Only six-time winners Toulouse can better Leinster's Champions Cup record, and back row Viliame Mata's experience could prove important for Bristol following the 32-year-old's return from injury.

Fiji international Mata helped his new club win 48-24 at Harlequins on Friday on his comeback from surgery to resolve a hamstring problem sustained during pre-season.

"I was so excited to get back out there," said Mata. "I pulled through well, did my time in rehab and I feel strong.

"I had a look at the clock - not even 20 minutes had gone and I was blowing so hard.

"It's always a dream to play the big teams from every league. It's going to be a massive one but I back the boys.

"We mentioned in the team meeting that it's just like playing Ireland because most of their boys play for Ireland - they know each other so well."

Bristol visit 2022 and 2023 European champions La Rochelle on 14 December, followed by a home game against Italian team Benetton on 12 January and a trip to Clermont Auvergne six days later.

Prop Ellis Genge and scrum-half Harry Randall are in contention against Leinster after being rested, while Lam has been impressed by his young players who have "stepped up and performed" on their way to 29 points from their first seven league games.

"This is what rugby is about - the team," said Lam. "Despite the challenge, we'll have a good chance.

"I've been blessed to win the Premiership [with Newcastle Falcons in 1998] and the Champions Cup as a player; they were both very enjoyable experiences, but the Premiership was only noted by the English, whereas the European Cup was worldwide.

"The stakes are high and your reputation as a club can be made or lost by the competition. This is the biggest stage in northern hemisphere rugby."