Darren Ferguson was left to rue two individual errors that left his Peterborough side facing a replay away at Sky Bet League Two Salford following a 2-2 draw.
Posh goalkeeper Nicholas Bilokapic twice gifted the visitors the lead, in the fourth and 69th minutes, with errors before towering defender Emmanuel Fernandez snatched an equaliser in the 93rd minute after being sent on to play upfront.
“I’m frustrated we’ve got another game and a journey up to Salford,” Ferguson said.
“We’ve already got Wigan on Tuesday so I didn’t want a replay. I ran the risk of losing the game towards the end.
“We were defending with just two players and the rest were upfront but in many ways, you don’t want to lose a game so you’re better off being in the cup and having a replay but it’s definitely a result I didn’t want.”
Bilokapic first played a pass straight to Stephen Mallan on the edge of the box to bury into an empty net and then allowed Zak Sturge’s backpass to roll under his foot.
Ricky-Jade Jones had pulled Posh level just 25 seconds into the second half, scoring in three consecutive games for the first time in his career.
Ferguson added: “We know the reason why we drew, there’s no other way of looking at it, it’s two individual errors. I don’t think they’ve any real chances in the game.
“The mistakes were momentum killers because we started the game really well and were on the front foot.
“The second came from nowhere. Before that, everyone thinks we’re just going to go on and win the game, even them probably.”
After coming so close to an FA Cup upset, Salford boss Neil Wood was left disappointed that his side could not get over the line.
He said: “It’s tough, they’re a really strong team.
“They had to really load it up with the subs they brought on at the end.
“We did ever so well and we’re a bit disappointed in the moments leading up to the equaliser, we probably made some mistakes. It feels like a defeat.
“I have high expectations for us and it’s probably a bit of disappointment creeping in but we have to put it into context.
“They are a really good team at the top end of League One, who have some excellent players.
“We dealt with their attacking players quite well and to get ourselves back in front and to get 90 seconds away from seeing it out, without doing so, is disappointing.
“We played some good stuff ourselves and defended really well so there are some real positives to take from the game.”