Johann van Graan admitted he was "gutted" for Chris Farrell after his latest injury setback, but is hopeful he'll make a swift return.
Farrell suffered a serious knee injury for Ireland against Wales last February. In his first start since that setback, he shone in the Pro14 win against Edinburgh but a week later the powerful centre was forced out of the Heineken Champions Cup clash with Castres at Thomond Park.
Munster still aren't sure just how serious the quad strain he suffered is, and Van Graan couldn't hide his disappointment.
"Chris Farrell is still going for some assessments but I don't see him being ready for this weekend [in Castres], which is a big loss to us. I'm gutted for Chris.
"He came back and gave a man of the match performance [against Edinburgh] and then in the warm-up pulled out. But that's rugby. We can't wait to have him back. Hopefully it'll be soon."
Munster saw off the reigning Top 14 champions 30-5 at the weekend but Van Graan said that scoreline doesn't begin to tell the whole story of a tough scrap.
They'll be braced for a sterner test when they head for France, and the head coach warned they'll need to improve.
"There's a lot of improvement needed for the weekend. You don't just go to France and get a victory. It's the French champions in Castres. It'll be a massive challenge for us but we're looking forward to it. We said we're going to enjoy this week. That's what these double-headers in Europe are about.
"We can only control what we can. We're sitting in a good spot in our pool. We can't control their mindset, the only thing we can control is ours. It's going to be a fierce battle, make no mistake about that. We'll get the bodies and the minds afresh and ready to go for Saturday.
"The scoreboard might not have said it but that was a fierce battle. You could see it in the kinds of knocks afterwards. The scrum was a battle, the maul was a battle, that breakdown battle was fierce at times.
"We've got only one task at hand, and that's to go to Castres and put in a very good performance. We're under no illusions about what it's going to take to go there and get a win."