In-form striker Saido Berahino cancelled out Gabriel Agbonlahor's 22nd-minute opener for the hosts but West Brom would ultimately pay the penalty for an error by Foster deep into stoppage-time.
The England keeper fumbled a loose ball and clattered into Matthew Lawton when trying to retrieve the situation, leaving referee Jonathan Moss with little option other than to point to the spot.
Christian Benteke calmly slotted home from 12 yards, but Pulis chose to focus on Foster's numerous impressive displays this term.
"People are talking about Ben - Ben's been absolutely fantastic for us all season," he said.
"He's saved us points, he's won us games. He's had an off night tonight, but there'll be no one at this football club who'll criticise Ben.
"Everybody has those days. I don't have to speak to him - there's no problems, he knows."
Pulis said West Brom were undermined by a lacklustre display during the opening 45 minutes.
"In the first half they were the better team," he said. "The best thing that happened to us in the first half was half-time.
"In the second half we were much better. They've had a shot from long range, which Ben has spilt, but I can't remember them doing too much more in the second half."
Late in the game, with the scoreline still at 1-1, Villa defender Alan Hutton was arguably fortunate to received only a yellow card for plunging his studs into Berahino's thigh.
Pulis was reluctant to add his voice to the current debate surround refereeing performances.
He added: "I've seen the Hutton challenge. There's been a lot of criticism and a lot of flack thrown at referees over the past couple of weeks.
"I'm not going to go there. I'll let other people decide what they thought about it and go from there.
"I don't want to criticise Jon or anyone else. I think they're getting enough stick as it it."
