The boss was happy that he still had Alan Lee at the club to score the equaliser. Palace were trying to offload the former Ipswich striker during the summer.
Warnock said: "Taking the 90 minutes into consideration I was delighted with the point.
"Even with 10 men we tried to push men forward but it's a decent result.
"Alan Lee had to work hard up there and he always has a chance if he puts in a shift like that
"We couldn't sell him for the money which we still owed Ipswich so we had to keep him. Barnsley made us an offer but Ipswich wouldn't do us a favour on the finance front so he stayed.
"We wanted to move him on but I said to him there'll always be a chance for him here, so well done Alan."
McCarthy saw red for two bookings after an afternoon of persistent fouling during a 90-minute duel with Posh striker Craig Mackail-Smith.
Warnock bemoaned the consistency of referee Kevin Friend and believes most decisions could have gone the other way.
He said: "In the old days that would have been a cracking battle between centre-half and forward but we are too finicky at the minute with too many directives.
"God knows what they will do with two more officials behind the goals."
Forward Victor Moses came on for a lively cameo which showed why he has been linked with a move to Wigan, but Warnock is confident of keeping him.
He said: "I would imagine we will keep Victor. We have not had any phone calls but everyone is aware of our situation so that could always change.
"I expect him to be here unless someone makes a silly bid on deadline day - which is always possible."
Peterborough boss Darren Ferguson does not expect to add to his squad before the transfer deadline but was adamant his side should have won after Shaun Batt put them ahead with a low drive after the break.
He said: "It was a missed opportunity to get our first win and it's two points dropped.
"We've never gone three games without winning since I've been here so it's something new to handle now it's five.
"Everyone will be shouting and screaming about our start but I have enquired about two or three players this week who were all on over £10,000 a week and we can't compete with that.
"Don't forget the size of this football club. We only get 8,000 fans so we are not a big club but we will compete at this level without a doubt."