The Senegal international made the switch from Rennes to Stamford Bridge for £22 million, being brought in to put pressure on the faltering Kepa Arrizabalaga.
Kepa’s string of high-profile errors last season continued into the new campaign as he gifted a goal to Sadio Mane in the 2-0 loss to Liverpool.
Mendy impressed in Tuesday night’s defeat to Spurs, making a good save from left-back Sergio Reguilon and dominating his 18-yard box.
Blues boss Lampard also commended his new goalkeeper’s performance, highlighting his aerial ability.
‘I thought he was very good,’ said Lampard after the game. ‘He made a couple of good saves. Came and caught a few balls.
‘Very very pleased with every part of his game.’
Chelsea have had a slow start to the season after their big summer of spending, winning just two of their opening five games in all competitions.
Next up for Lampard’s side is a tricky test against Crystal Palace at Stamford Bridge on Saturday.