McManaman has suffered ankle ligament damage which will keep him out for between four and six weeks, Pulis told the media on Friday.
With central midfielder James Morrison sidelined for up to two months with a knee problem and Darren Fletcher struggling for full fitness, West Brom are set to turn to Sandro in a bid to bolster their squad before transfer window closes.
"We are interested in Sandro but nothing has been done yet, that's ongoing. Whether we can do a deal or not we will have to wait and see," Pulis said.
"We are working on it, if we can get a deal done, we will get a deal done and if we can't, we can't, and we will have to move on.
"It is potentially a loan with a view to a permanent if we can do it."
West Brom face two key games against Premier League strugglers Swansea City and Newcastle United next week, but Pulis insists he will field a strong side against Peterborough United in Saturday's FA Cup fourth round.
"It’s a three-game week but I have made my feelings about this competition very clear – I will be fielding a strong team to win the game," he said.