The France international played only 17 minutes of the Blues' 4-0 Premier League defeat to Manchester United at Old Trafford on Sunday as he was short on fitness.
Lampard says the 28-year-old sustained another minor problem in that match and is therefore facing a race to be ready for the meeting with Liverpool in Istanbul on Wednesday.
"Kante was purely because he had an injury. I am very aware of how important he is," Lampard told a news conference, speaking about the former Leicester City star's omission from his last starting line-up.
"He picked up another small injury in the game, so we are assessing that."
Lampard insists there will not be any wholesale changes to his team for the showdown with the European champions despite the disappointment of the United result.
"I pick the best team to win the game, regardless of age," Lampard said. [Mason] Mount deserves his chance on merit; I won't fear to play young players.
"In terms of how we set up, I really liked some of our aggressive off-the-ball work. We have to be adaptable and respect the strengths of our opponents. There may be subtle changes of our approach."
Wednesday represents a chance for Lampard to win his first piece of silverware as Chelsea boss in the form of a trophy he did not manage to lift in his playing career, having been beaten 4-1 by Atletico Madrid in the 2012 match and by Bayern Munich on penalties a year later.
"It means a lot to the club," he said. "I lost two, one in poor circumstances, having won the Champions League and we were far off that game.
"It is important to give everything to win it. It is another trophy for the club."