Lampard says the midfielder is now working with the club's youth teams.
He said, "He is actually training now with the Under-16s, with the Under-18s, and progression to the under-23s in a pretty short space of time. the sooner he can be back training with us, the better, but we train with a real intensity. When you've been out for a long time, it's very standard you bring him through the Academy years.
"There's a different look on Ruben's face. He is more smiley and happy which I understand. It's been tough for him. He's not one who walks around with his head down or creates a negative atmosphere, but it's a lonely place. That's for everybody. He's integrating more towards us which is great news for all of us.
"The player he is, the lad he is, it can be easily forgotten from the outside we have missed a hugely influential player. If he can be training with us after the break, it might still need some competitive games but he might not be far away."