Sean Morrison left St Mary’s on crutches on Saturday afternoon, as a precautionary measure after sustaining an ankle injury in the 1-0 defeat to Southampton.
Brian said, "We've been unfortunate with injuries, I'm not one to really moan about it but we've had long term ones with the likes of Alex McCarthy. But that's why you have a squad.
"I'm not sure Morro will be available Tuesday, it's his ankle and he's on crutches as a precaution. Pavel is out, Jem, Jimmy and so on. Come Tuesday we'll be ready again.
Elsewhere, Jem Karacan has begun light training after suffering knee ligament damage in our clash with Liverpool earlier in the season, whilst Jimmy Kebe and Pavel Pogrebnyak are also receiving treatment – with the Russian striker having picked up knock in a friendly clash with Stevenage earlier in the week.
Chris Gunter has also not featured since our trip to Wigan, after picking up a hamstring problem in training.
Royals goalkeeper Alex McCarthy is set for a spell on the sidelines after undergoing successful shoulder surgery earlier in the week.
The 'keeper, who turned 23 on Monday, underwent the operation in London after picking up the injury in the very last minute of our Barclay Premier League draw at QPR last month.
Head of Sports Medicine Luke Anthony said, "We had an encouraging MRI scan on the Monday after the QPR game, then we saw a shoulder specialist the following day and he was also positive that Alex should be able to recover with a conservative rehab programme. But it soon became clear that the structural damage wasn't going to improve without surgery, so we saw another consulant late last week and then on Monday Alex successfully had his labrum tissue repaired.”