The striker has been injured and out of favour under the new manager at Aston Villa this season but returned to the team to score against his former club Ipswich in the FA Cup
Bent has been sidelined with a hamstring injury in recent weeks and struggled to win a place in the Villans XI before that due to the good form of new signing Christian Benteke.
The 28-year-old grabbed the equaliser after Michael Chopra had opened the scoring at Villa Park, though, and Andreas Weimann added a second to secure their safe passage into the fourth round.
|13/8||Aston Villa are 13/8 with William Hill to be relegated this season
"His overall game was very good - his whole work ethic, the way he played. But his general game was very good."
Bent had not scored since September 30, but has now bagged four goals in his last five appearances in the FA Cup.
Lambert will now have to decide whether to include Bent in his squad for the first leg of the club's League Cup semi-final against Bradford. on Tuesday.
"Considering he only really trained with us yesterday, it was a big, big effort from him," Lambert added.
"We left out a few lads to give them a break and I was delighted with everyone that came in. I thought it was a massive effort."