In recent seasons Toulon and Saracens have been perennial visitors to the latter stages of the Champions Cup, with Mark McCall's men winning the competition last year.
Like Sale Sharks, Scarlets are the undoubted underdogs to progress from their pool to the knockout stages but Williams is refusing to wave the white flag and is relishing the challenge of facing the best in Europe.
Scarlets start with a home game against Sale Sharks on Saturday and Williams knows it's crucial the Welsh club get off to a flying start in the competition.
"It's a massive test and, you know, you want to be playing against the best teams and we've got some decent teams in our group," said Williams.
"We're the only region in the competition this year, so we're flying the flag a little bit for Wales and we want to do well.
"There's massive history behind this competition and we want to get off to a good start.
"Hopefully we can get a good crowd down for the Sale game and hopefully we can get a win.
"These games are massive challenges, there are no easy games, but as I said you want to be playing against the best teams and you want to be measuring yourself against them."
And Williams admits he is particularly looking forward to the clashes with Toulon and Saracens in pool qualifying - two teams packed with international names and star quality.
"We've got some younger boys who would have played in the competition last year as well and hopefully they would have learned a lot from that and can improve this year," he added.
"Saracens are a massive challenge; they've shown that in the last 12 months - I'm looking forward to that one. We're going have to be at the best we can be if we want to stand a chance of beating them.
"But we have to take it game-by-game and hopefully we can get a win against Sale and then target Saracens and Toulon."
European Professional Club Rugby (EPCR) is the organiser of the European Rugby Champions Cup, the European Rugby Challenge Cup and the Challenge Cup Qualifying Competition. Follow all the excitement of another thrilling season of European action at www.epcrugby.com.
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