Lescott joined West Brom on a free transfer from Manchester City in June, but has struggled to shake off a knee complaint.
The 31-year-old will miss Saturday's season-opener against Sunderland and fellow centre-back Gareth McAuley (calf) is also in doubt.
But despite the temptation to rush Lescott back, as West Brom – one of the favourites to be relegated – look to start well, Irvine will be taking no chances.
"It's important that we make sure we bring Joleon back in at the right moment," Irvine told West Brom's official website.
"He was desperate to get back in and make sure he was ready for the start of the season and probably, with hindsight, he came back a little bit too early.
"But what do you do when a senior player is that desperate to play and says he's okay? It's difficult for the medical people to override that.
"This time we're being a little bit more cautious to make sure that he's definitely ready for when he comes back.
"We expect him to train with the group next week and we'll take it from there.
"But the most important thing is that Joleon is available for most of the season, so if he misses a couple of games now, so be it."
West Brom broke their transfer record in the close-season to sign Brown Ideye from Dynamo Kiev.
The Nigerian forward is expected to feature at The Hawthorns on Saturday, despite a pre-season blighted by visa issues, but Irvine has been frustrated by the club's inability to secure other key signings.
"There are all sorts of things going on behind the scenes and [director of football administration] Richard [Garlick], [technical director] Terry [Burton], the recruitment staff and the chairman are all working extremely hard behind the scenes," he said.
"But it's extremely difficult because you come up against dead ends on a number of occasions.
"I went to a managers' meeting and Paul Lambert, Harry Redknapp and Steve Bruce were all saying the same things and have the same problems."
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