The former Manchester City defender will sit out the Baggies' Premier League opener with Sunderland on Saturday due a knee injury.
Lescott took a knock in West Brom's pre-season clash with Nottingham Forest, and Irvine is aware that rushing him back to fitness may make things worse.
"It's important that we make sure we bring Joleon back in at the right moment," he told reporters.
"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.
"This time we're being a little bit more cautious to make sure that he's definitely ready for when he comes back."
Saturday's encounter at The Hawthorns is scheduled to kick off at 3pm.