The Brazil international joined the club as a free agent having seen his contract with Paris Saint-Germain expire.
Now 36, the veteran has slotted seamlessly into the Chelsea rearguard and has quickly established himself as an integral member of the side.
While he gave a strong account of himself defensively in the 3-0 win over West Ham on Monday, he also notched the opening goal with a fine header from a Mason Mount corner.
“I remember playing in the 36 and I couldn’t play like he’s playing – it hurts,” Lampard told Sky Sports.
“I knew he was a top player – he’s been a great player for a number of years – but he’s handled the pressure of the Premier League. I shouldn’t have been surprised but he has exceeded my expectations.
“His quality and the reading of the game, he really wants to beat his opponent to every ball and to every header. He’s really studious about the game and when he’s finished playing he can go on to do whatever he wants.
“He’s been a really great addition on and off the pitch.”
Lampard was also pleased with Tammy Abraham’s contribution as the striker scored two goals to justify his selection ahead of Olivier Giroud.
“West Ham are very solid and well organised and I felt Tammy’s natural ability to return in behind would help us,” he said. “Tammy came up trumps, but that’s no slight on Ollie, who produces when he plays.
“The game was hard. We started well. We didn’t get so much ball and stopped playing a little bit. You’re delighted when you get that second and third goal. It wasn’t vintage. The best part for me was the character coming back from two defeats.”
Victory puts Chelsea fifth in the standings ahead of a Boxing Day trip to struggling Arsenal.