"It looks as though, from the provisional scans we have done on Tuesday, that Paolo has had a little cartilage tear.
"So we are going off to see a specialist in Italy to confirm the news and if, indeed, he concurs, it is quite possible that Paolo will need a small operation, an arthroscopy, to repair it.
"Clearly, until you have a look, you can't be certain, but these things can take eight weeks or more depending on the situation.
"We hope it will be a speedy and a full recovery and there is no suggestion it won't be; the time factor will be the 'if' - but the recovery won't be a problem.
"He has not had previous problems with his cartilages and it is not a particularly big tear, but obviously it is an injury and we need to clear it up."
If that two month lay off is confirmed, Glenn - already sweating on the fitness of Fredi Kanoute, who has been out of action for nine weeks and is not likely to play at Middlesbrough on Saturday - will seek urgent reinforcements come January.
Still coming to terms with a defeat against Southampton on Monday in a game he feels should have been won, he candidly admits:
"It is a huge disappointment; it is hard to put into words to describe how everyone felt about the game and the end result after a performance like that - it was a real bitter pill to swallow.
"But the scan yesterday which will lead to further tests is a double whammy, and if a tear is revealed and he needs a cartilage operation that could keep him out for a fair period.
"He has been very influential in games this season when we have picked up Premiership points, and, although we are initially hoping it will still be only two or three weeks, it could be much longer.
"That reduces us up front to Fredi when he is fully fit, Jermain Defoe, Ian Pearce who battled manfully on Monday and overall did very well, and Titi Camara."
Glenn has already made it clear that he wants to bring in back up for Fredi Kanoute in terms of a physical front man who can hold the ball up, but if Paolo is out for any length of time he will need to double his targets.
"We would need to squeeze it to bring in two strikers - we have got to make it happen, and we are working overtime on it.
"This could shift the emphasis, and I am in Europe on Wednesday looking at a player - we need the firepower.
"For the moment, we are holding our breath, and if Paolo is only out for three weeks then one striker will be enough.
"But if not, we have got to make it happen with two because when that transfer window closes you are on your own for the rest of the season.
"We need to be pro-active in the market to bring people in in early January; the squad needs a lift with two or three fresh faces to give us belief and confidence.
"It is a massive problem and, as if it isn't bad enough that we haven't won at home yet, this happens."