Lolley hurt his right lower leg in a challenge from Isaac Hughes in the second half at Sky Stadium on Sunday and attempted to play on, but later went down with no players around him and had to be helped off in the 57th minute.
Coach Ufuk Talay didn't know how serious the injury was.
"It's his ankle. I think at the challenge at the corner in the second half on our left-hand side," Talay said.
"I think there was contact but then when he landed he sort of like twisted it. We're not too sure - we'll have to get back and scan it and go from there.
"He's had a topsy-turvy season this year, Joe. He's been out with a hamstring injury, we got him back and we're trying to build him back into form with game time.
"There's no other place we can play him besides the games we have on the weekend and then for this to happen. I don't want to be negative about it, I hope it's not as bad as we think it is, but we'll go from there."
It soured a day where Alexandar Popovic's 49th-minute goal lifted Sydney to third on the table, after Wellington controversially had a penalty overturned earlier in the match.
A week after Joshua Oluwayemi conceded a howler and was hooked at half-time in a loss to Auckland that led to Giancarlo Italiano's resignation, the goalkeeper was backed to start by interim boss Chris Greenacre and performed well.
Wellington were awarded a penalty in the 32nd minute when Rhyan Grant was ruled to have pushed Kazuki Nagasawa in the back in the area.
After a VAR review, referee Tim Danaskas overturned his decision, ruling there was no foul.
Phoenix skipper Alex Rufer and Greenacre wouldn't buy into discussion of the call while Sydney were adamant it was correct.
Sydney took the lead when a corner spilled out to Ben Garuccio, who played a one-two with Grant, beat a defender then squared the ball for central defender Popovic to tap home.
Wellington pushed for an equaliser and Harrison Denevish-Meres backpedalled to make a sublime save to deny Luke Kelly-Heald's looping header in the 85th minute.
"I asked the players for a reaction, but professionally and personally - and I think you saw there at the end - they've given everything," Greenacre told Sky Sports NZ.
"So I can't ask any more of my players."
Sydney next host Melbourne Victory on Saturday while Wellington travel to face Adelaide on Friday.
20°C