Experienced defender Bartley endured a derby evening to forget as the visitors ran out 3-2 winners at The Hawthorns with Scott Hogan’s hat-trick doing the damage.
Bartley, 31, made his 150th appearance for the club but was subject to personal boos from home fans after Hogan benefitted from an error to make it 3-1 to Blues.
The defender missed an interception in the build-up to Hogan’s second in an error-strewn contest and now Bruce has called on him to rise to the situation and battle back from a difficult position as the Baggies find themselves down in 20th, only outside the bottom four on goal difference.
“I don't want to make excuses for him. He's had a really difficult pre-season,” Bruce said.
“The reason I took him off in the last couple of games was sheer lack of games, especially for somebody like a centre half.
“He's got to deal with the situation, he's an experienced pro. He's played for a long time.
“He's got to earn their trust back, and the only way he can do that is by getting as physically well as he can be and knuckle down and get on with the job.”
Albion are thin on the ground when it comes to central defensive options owing to the injury to Semi Ajayi, who had surgery on his ankle.
Cedric Kipre and Caleb Taylor were allowed to exit the club this summer on loans to Cardiff and Cheltenham respectively.
Martin Kelly and Erik Pieters were both brought in as free agent cover at full-back and centre-half. The latter made his debut from the bench last night but Kelly is not available until after the international break, which follows Saturday’s trip to high-flying Norwich.
Bruce could also look to drop one of midfielders Jake Livermore or Okay Yokuslu into the back four should he opt to take Bartley out of the firing line.
The boss added: “Well he's an experienced player, he's gone through a difficult period.
"He's got to do the basics better. But more importantly, rather than mine, he's got to earn the supporters' trust.”
Bruce's side last night conceded the first goal in a game for the eighth time in 11 games this season and the fifth game on the spin. Albion did not heed the warning when Troy Deeney skewed a golden chance wide for the visitors inside a minute.
The manager referenced 'mentality' when surmising the issue and agreed that confidence and fear are an issue.
"Yeah, absolutely. It's baffling," Bruce said when asked about that record.
"And to be fair they should've scored after a minute.
"That didn't wake us up either. That is a real frustration with us. Every time we play we're a goal down after 15 minutes, that doesn't help, eh?
"We'll look at that and see if we can change something, but that's a mentality thing, I would think."
He added: "I agree, the problem is too we've kept one clean sheet all season.
"Again we've scored twice, even on a bad night we scored twice – we might have been a bit fortunate with the second one it could've been outside (the box), so the tell me.
"Expected goals we're at the top of the league, but our defending was...I haven't seen as bad a goals to give away than I have tonight."