Sissoko clashed with Glen Johnson in the 83rd minute, earning a second caution for the incident at Anfield which occurred with the visitors already trailing 2-0.
Newcastle went on to lose by that scoreline - their fifth consecutive league defeat - but Carver said Sissoko was lucky referee Lee Mason did not issue a straight red, which comes with an automatic three-game ban.
Carver also lauded his side's overall performance, and said Sissoko's dismissal with seven minutes to play cost them a chance at fighting back late.
"They actually came out the second half and went on the front foot again and for me, in my eyes, dominated some parts of the play without actually opening up the back four," Carver told a news conference.
"But then the sending off does affect you. You go down to 10 men.
"I think we were slightly fortunate that he got a yellow card, because it could have been a straight red. I'll be honest, and I've said that to Moussa.
"I am quite straight, and I won't defend anybody if it's undefendable (sic) - he should have got a red, he got a second yellow.
"Now he'll get a two-match ban because it's his second sending off, so we got away with one there."
Carver added Sissoko would likely be hit by the club with a financial sanction, after Newcastle finished with less than 11 men for their third consecutive trip to Anfield - something Carver said he warned against pre-match.
The coach said Newcastle's fans should be content with the response of his side, despite extending their losing streak.
"I think you [the fans] got a response. Obviously, we didn't get a result," Carver said, when asked for a message to the fans.
"But I think there was a response after last weekend. Anything would have been a response, been better than what we saw last weekend against Sunderland.
"We've now got Fabricio Coloccini coming back into the side to strengthen that defence.
"There was a lot of positives to take.
"A lot of people thought we were coming here tonight and expected us to get a hiding. I don't think we got that.
"We held our own for long periods of the game against a top side, against a side who have got an abundance of talent."
Carver said midfielder Siem de Jong would play in a reserves fixture in mid-week as he continues his return from a collapsed lung, while Rolando Aarons (hamstring) would be assessed.
He added it is unlikely the pair would be fit to appear in Newcastle's hosting of Tottenham on Sunday.
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