Lock Dave Attwood says Bath did not show they were up to the challenge of playing in the European Champions Cup in their defeat at Glasgow.
The Pro12 leaders won 37-10 at Scotstoun Stadium on Saturday in their Pool Four opener.
Attwood told BBC Radio Bristol after the game: "They came out and played like they wanted to be a part of the Champions Cup.
"I don't think the players representing our club did that - myself included."
Jonathan Joseph scored Bath's only try of the game, while Glasgow ran in five to secure a bonus-point victory.
Attwood continued: "We're going to be bitterly disappointed with that, not necessarily the result but the nature of it.
"They really wanted to step it up and be a part of this competition and we didn't."
|Bath's European Champions Cup fixtures|
|Sat, 25 October: Toulouse (H)|
|Sat, 6 December: Montpellier (A)|
|Sat, 13 December: Montpellier (H)|
|Sat, 17 December: Toulouse (A)|
|Sat, 24 January: Glasgow (H)|
Premiership Bath made several changes to their forward pack, with front-row duo Nick Auterac and Henry Thomas making their first starts and lock Dom Day playing as blindside flanker.
The club's back-row options are depleted because of injuries to Francois Louw, Matt Garvey, Carl Fearns and Alafoti Fa'osiliva, while Leroy Houston is serving a three-week suspension.
However, Attwood insisted changes to the team should not have impacted their performance.
"It didn't make things easier but we had first-team players out on the pitch," he added.
"As far as I'm concerned the people on the pitch knew their roles. Throughout the entire squad we didn't want it enough."
Bath return to the Rec next weekend to host Toulouse, who beat Montpellier 30-23 on Sunday, and Attwood says they must be at their best to get a result.
"If we're going to feature at all in this competition we really need to step it up," he concluded.
"Next week we need to make a good account of ourselves and I expect a big reaction."