Following errors in recent outings, the Swede was dropped for yesterday's trip to Tottenham Hotspur, which the Baggies won 1-0.
However, Irvine has reassured the 31-year-old that he remains a firm part of his plans for the coming months.
"Jonas wasn't injured. I spoke to him on Saturday and told him what my intentions were. That wasn't easy because I have a lot of respect for Jonas. He's a top professional and a very good player," the Scot told the Express & Star.
"I had some big decisions to make and I had to look people in the eye to tell them why I was making those decisions. That's not easy but it's part of my job. Jonas will remain a very important member of our squad."
Olsson joined West Brom from N.E.C back in 2008.