Foster, signed from Manchester United for £6 million last summer, has had an outstanding first campaign at Blues and helped them to win the Carling Cup.
The England goalkeeper was substituted with a dead leg and a back spasm during last weekend's five-goal mauling at Liverpool. But he has made a rapid recovery and will be looking to aid Blues in securing the win which should ensure top flight status for another season.
There has been speculation suggesting Foster could become a wanted man this summer after his fine form.
But McLeish said: "If our players are interesting other clubs, then it means we are doing something right. Is there speculation about him? I don't read the papers or tune into TV channels.
"Ben has undoubtedly saved us a lot of points. That is one of the reasons why you've got to make sure your keeper is right. It is the key. I think Ben is one of the best keepers in the Premier League.''
McLeish is relieved to have Foster back for such a crucial game, saying: "Ben will be okay, he will be back amongst the posts. He had some problems last week no doubt about that.
"It is never a great situation when you have to substitute your number one keeper in a game. He hobbled off the team bus last Saturday night and he also had a spasm in his back which rendered him practically immobile. If you had seen him then compared to now, he is a different animal and he will be fine.''
McLeish is looking for a positive response from his side after conceding eight goals in losing to Chelsea and then Liverpool.
"Listen, we are smarting from that Liverpool defeat. We were all annoyed at the end of the game. We had our say in the dressing room but it stays there and we get on with it. We made some individual errors, we were a bit open as a team, so I've got to take some of the blame for the setting up of the team.
"We've got to do everything we can this weekend for the highest performance level possible. We've been quite good at bouncing back from setbacks.
"Some people might say we are okay. I wish that was the case but at the same time we've got to get on with the job. There is pressure there, there is pressure on all of us in the bottom half of the table, but it is part of the job, and part of the solution is to handle that.
"If it didn't matter, there would be no pressure, but it does matter and we care deeply about the club's Premier League status. We will be doing everything we can to get over that line as quickly as possible but there are no guarantees.''
McLeish has plenty of respect for Wolves boss Mick McCarthy and knows a Birmingham win will send Sunday's opponents closer to relegation.
But he admitted: "You don't look at it that way. You look at the situation from your own point of view. We've got to try and get safe and climb that league with the games that are left. There are four games left and we've got to try and take as many points as possible and doing everything we can to do that.''