The 19-year-old enjoyed a promising start to life in the Blues’ first-team last season, making 11 Premier League appearances in a breakthrough campaign.
However, Gilmour was forced off in the 3-2 win over Crystal Palace in July and required surgery on his knee, putting a swift halt to his rapid progress.
But, speaking ahead of Chelsea’s Champions League clash against Sevilla on Tuesday, Lampard provided a positive update on the Scotland youth international’s fitness.
‘Billy’s working really well, he’s probably three weeks away from his return,’ Lampard said.
‘He’s working outside on his own with the physios still, we hope that he’ll integrate with either ourselves or the Under-23s to get some training minutes.
‘So hopefully three or four weeks, probably the other side of the next international break all being well.’
‘We’ve had a few of the young come through this year and that’s given me great pleasure,’ Lampard said in April. ‘They’re great to work with, they’re like sponges who want to come in and learn.
‘Billy probably gives me as much pleasure as anyone. When you look at Billy he’s quite slight in terms of his size, he’s young, he’s quiet, he’s polite, but Billy moved over to the first team building a while ago because he had to. He trained at such a level.
‘If you have possession in training or a game or a simple passing drill, you’re talking about attitude and doing the basics right. In the modern day it can get lost a little bit. Can you do the real basics right? Billy does them day in, day out.’