Goals from Shane Duffy and James Forrest helped Celtic come from behind to win 2-1 at St Mirren and stay in touch with Rangers at the top of the Scottish Premiership.
The champions fell behind after just three minutes at the Simple Digital Arena as Lee Erwin scrambled home his first goal for St Mirren.
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However, the visitors responded to that setback to go in ahead at the break thanks to well-taken headers from Duffy - the recently signed centre-back's second in two games - and Forrest.
Neil Lennon's side held on for the win despite Odsonne Edouard's second-half penalty miss to close the gap on Rangers at the top of the table to three points with a game in hand.
St Mirren, meanwhile, stay in seventh.
How Celtic hit back to move up to second in the table
The match took place against the background of continuing Covid-19 issues which had affected the Paisley club.
The home side had emergency loan goalkeeper Zdenek Zlamal in goal again as first-choice 'keepers Jak Alnwick and Dean Lyness remained out after recording positive coronavirus tests.
Third-choice goalkeeper Peter Urminsky, left out of the 3-0 defeat by Hibernian at the weekend as a precaution, started on the bench.
Joe Shaughnessy, Dylan Connolly and Junior Morais were back in the team along with Erwin.
Fourth-choice Zdenek Zlamal continued in goal for the hosts after No 1 Jak Alnwick tested positive for coronavirus.
Meanwhile, Celtic made four changes to the side that won 5-0 at Ross County on Saturday. Patryk Klimala was brought in, while fellow forward Albian Ajeti dropped to the bench. And Greg Taylor and Hatem Elhamed also started, as did Ryan Christie in midfield.
Celtic boss Neil Lennon also made four changes as he brought in Hatem Elhamed, Greg Taylor, Ryan Christie and Patryk Klimala, the latter coming into the side for his first start this season to partner Edouard.
It was the home side who struck first when Jamie McGrath's corner from the right was flicked on by Shaughnessy and Erwin scrambled the ball over the line from a yard out.
Celtic's inevitable response saw Saints pinned back and in the 19th minute Edouard headed wide from a Forrest cross.
However, moments later, Republic of Ireland international Duffy was more accurate from Christie's free-kick from wide on the right as he powered in a header past Zlamal, undoing all Saints' good work.
Celtic's pressure was relentless. Zlamal made good saves from Callum McGregor and Edouard but had no chance with Forrest's well-placed header, with Christie again the provider.
St Mirren had to come out of their shell and there was a penalty claim for handball against Duffy in a packed Celtic penalty area turned down by referee John Beaton.
The Hoops carried their threat into the second half.
McGregor came close with a low drive from 16 yards, Zlamal pushed a dipping Edouard free-kick from 20 yards past the post and then saved a long-distance effort from Christie.
Celtic kept the ball zipping around as St Mirren retreated to the edge of their box in compact shape, but a foul by McGrath on Christie had Beaton quickly pointing to the spot, only for Zlamal to dive low to block Edouard's penalty.
Still, Celtic dominated possession but the Buddies keeper again proved his worth with another fine save from Christie's 20-yard drive in added time.
What the managers said
Jim Goodwin: "People will be sick and tired of my whining voice but I am disappointed that we didn't get a penalty in the first half.
"I'm not for one minute suggesting that Shane Duffy deliberately handled the ball but he definitely did handball it.
"He lost the flight of the ball, it hit his left arm, and in doing so it actually stopped the ball going through to Richard Tait.
"We would have had an opportunity to put the ball in the back of the net, a difficult one at that but it still would have been a good chance.
"So we're not getting the rub of the green at the moment. People tell me these decisions even themselves. I'll (not) hold my breath on that one but you know that's another one that went against us.
"Similar to the one on Saturday, at two nil, a stonewall penalty denied when (Ryan) Porteous almost catches the ball and then Martin Boyle punches the ball into the back of the net for the third.
"So I think maybe the conversation we should all be having is where are you going to find the money to get VAR."
Neil Lennon: "It's difficult because there are no supporters. I think it's really difficult for them, especially at a big club like ours.
"You get a head of steam up in a game and normally you get the atmosphere crackling.
"It gives the players a lift and there is none of that at the minute. If the goalkeeper makes a great save, the crowd get up.
"You win a corner and it's an important facet of the game. We are missing all that at the minute.
"So there is a bit of adaptation, no question subconsciously that is a big miss for them.
"It's not an excuse like, but even for me winning 5-0 at the weekend (against Ross County) - there is not a big crowd there to enjoy it and enjoy the atmosphere.
"Even tonight would have been great. Tannadice would have been great. We are adapting as best we can and as well as anyone."
St Mirren travel to Dundee United, while the champions entertain Livingston at Parkhead, with both Scottish Premiership matches kicking off at 3pm on Saturday.