Chris Powell blasted Charlton's first-half display in the 2-2 FA Cup draw with Oxford as their worst since he took over three years ago.
League Two United raced into a two-goal lead as they attempted to make it third time lucky in a tie which had been postponed twice due to the state of Charlton's pitch.
But after a half-time dressing down by Powell, the Championship side hit back to secure a replay through goals from Michael Morrison and Yann Kermorgant.
"That was easily the worst 45 minutes since I've been manager here," said Powell.
"I told them I don't ever want to see that again from them. It was unacceptable.
"Forget the pitch, it was a side that didn't play to our standards and didn't compete.
"I don't know why, I didn't ask questions, I just did all the talking and got a response."
The playing surface at The Valley passed an inspection but still resembled that of a lower-league ground on third-round weekend.
So perhaps it was no surprise that Oxford, still a Conference club four years ago, adapted better to the conditions early on.
They took a 13th-minute lead through Johnny Mullins' deflected shot and doubled their advantage through Scott Davies after a mistake by Jordan Cousins.
Charlton were booed off at half-time but rallied after the break and Morrison pulled one back with a header before Kermorgant's acrobatic volley hauled them level 10 minutes from the end.
The hosts could have won it in stoppage time but Callum Harriott's goalbound header was nodded clear by David Hunt.
"The crowd showed their displeasure at half-time which is absolutely correct and we turned it around and nearly won it at the end," added Powell.
"It's the FA Cup and there are always strange results and we were nearly on the end of one, but we put it right, we are still in the cup and we'll go again at Oxford."
Oxford could be forgiven for thinking their best chance of progressing to a fourth-round trip to Huddersfield has gone.
Not only did they deal with the tricky surface far better then Charlton, but they now face a replay at home where they have won only four times all season.
"Do I fancy us now - not with our home record!" admitted manager Chris Wilder.
"I'd rather come back here. The pitch was a leveller for us, in terms of the quality Charlton can produce, and we managed to make a tie of it.
"I sympathise with Chris Powell, he's got an excellent passing team and it's a tough gig to play on that every other week.
"But credit to them for the character they showed in not wanting to get knocked out by a team two divisions lower."