George Friend was substituted in the 3-1 defeat to Swansea on Saturday, picking up a groin injury mid-way through the first half and missed the trip to Bolton on Tuesday night.
With Boro lacking anther recognised left-back, midfielder George Saville deputised at full-back against Bolton in the 2-0 win, with Pulis confirming Friend will miss the final five games of the season.
“He’s torn a muscle right up in his groin” Pulis said.
“I don’t think he’ll be fit for the rest of the season, which is a massive disappointment.”
“To lose Wingy and George, they have been two big players and important for the run-in, but they’re not there so we have to get on with it.”
With Friend unlikely to play again this season, it’s still early day’s with regards to Lewis Wing’s injury.
When asked if there’d be a chance of Wing playing again this season, Pulis said “first and foremost, let’s hope and pray that everything goes alright for him.”
Wing's operation was carried out by the surgeon who treated Darren Randolph's hernia last summer as Boro were pleased with the way Randolph recovered from that operation, with Boro keen to make sure Wing was seen by the same specialist.