Millwall manager Gary Rowett refused to use the ongoing pandemic as an excuse for the 2-1 defeat to Coventry despite eight of his players contracting Covid-19 in the last two weeks.
Rowett did however admit the virus might have been a factor in the Lions' lacklustre display and recent poor form that has seen them win just one of their last 13 games.
Millwall fell 2-0 down inside the first 25 minutes at The Den, where they have won only once this season, as they failed to register a shot on target in the first half.
But it was too late to salvage anything from the game as Millwall continue to slide down the Championship table.
"I thought it was a poor performance and to come in 2-0 down at half time probably flattered us," said Rowett, whose side had Murray Wallace sent off in stoppage time.
"Coventry were excellent and showed what it takes sometimes to get a result. They were prepared to work their socks off and close down and get in our faces to make it difficult for us.
"I don't think we did the same to them and it was a performance for me that lacked bravery. We were a yard off the pace all over the pitch.
"When we score we suddenly want the ball and start looking quite bright with a bit of zip about us but I've just said to the player we have to do that at 0-0 because that's how you win games.
"The last 14 or 15 games we've not been good enough and it's not acceptable. We've had eight players with Covid-19 in the last two weeks and five of them started today.
"I don't know what the effect of that is but certainly we looked a bit off the pace physically. It certainly wasn't the only factor though and it was a poor performance today – we deserved to lose by more."
Mark Robins had a much more enjoyable evening in the away dugout as his Coventry side earned their first win in four.
Jordan Shipley looked a constant threat and could have finished the afternoon with a hat-trick had he taken his chances.
"I thought we were brilliant, really, really good," said Robins. "We could have won by a lot more but Bartosz Bialkowski is a top goalkeeper who made some really good saves and they made some really good blocks in front of goal as well.
"The first goal was a brilliant shot from Shipley that hit the post and bounced in off a defender and that probably needed to happen to loosen the shackles.
"And from then, Shippers (Shipley) was unlucky with a screamer of a left foot that hit the inside of the upright and came back out and another one – the volley that got blocked and there was a shout for a penalty.
"Callum O'Hare had a brilliant chance where he could have finished it off, and Ben Sheaf in the first half where he should have scored.
"So we created a lot of opportunities and that was because we played with a tempo. So it was a really good performance."