Alan Pardew conceded Crystal Palace lost momentum after Yohan Cabaye's penalty miss in the 1-0 Premier League loss at his former club Newcastle United.
The FA Cup finalists were the stronger side in the first half, with Newcastle indebted to goalkeeper Karl Darlow for keeping them on level terms.
Andros Townsend netted a superb free-kick after 58 minutes - a goal that lifted Rafael Benitez's side out of the relegation zone at Sunderland's expense, thanks to Darlow keeping out a tamely struck spot-kick from Cabaye after Moussa Sissoko was adjudged to have handled the France international's corner.
"It was tight. First half, okay, I thought we were the better side and maybe in a little spell we had a couple of moments where we could have scored but we didn't," Palace boss Pardew told Sky Sports News.
"In the second half they came out and reacted. They had a good spell and scored right at the end of it, which was a plus for them.
"They were tight - a better Newcastle side than we played earlier in the season for sure [Palace won 5-1 at Selhurst Park in November].
"We missed the penalty and that was when the game died for us. It would have made it a very interesting end if we'd scored.
"We don't miss many and it was an unusual one. He hasn't hit it as he would have liked and gave the goalkeeper a chance."
Pardew felt he benefitted from a reserved reception on his return to St James' Park and praised his former club for their efforts in battling the drop.
"It's a tough result for us and it's a great result for Newcastle," he said. "I'm pleased for the fans and the players that I managed here, and the staff. Good luck to them.
"I think I've tried to be respectful since I've left, I tried to be respectful here and do the best job that I could under the regime I was given."
Pardew praised his team's commitment throughout the match that he said undermined Sunderland manager Sam Allardyce's pre-match suggestion that Palace would have been "on the pop" after securing their place in the cup final.
"I thought it was a bit of a pre-historic comment, really," he added. "I don't know if those days are done. I've got about three of my players who don't drink so I didn't really get that."