The 28-year-old has been struggling with a knee injury he picked up on the eve of Chelsea's 4-1 Europa League final win over Arsenal in May and faces a race against time to recover for the start of the new Premier League campaign.
Kante is yet to feature for Lampard's side during pre-season and the decision was taken to send the France international home before Chelsea beat Barcelona 2-1 in the Rakuten Cup friendly clash in Saitama.
"He is okay," Lampard said in his post-match press conference.
"It was a decision that I made because I felt that him being here, with the facilities and the moving and travel that we have been doing, it probably wasn't the most beneficial for him.
"He went back, has had a few days at Cobham (Chelsea's training base), working well, progressing, so hopefully by the time that we get back at the end of the week I will sit down with the doctor and hopefully know that he will be back with us very soon."