The 24-year-old, on loan from PSG, hasn't featured for the Potters since November 29. He has spent time in his native Spain to look after his ill son.
Now back training at Stoke, Lambert has opened the door for his return to first-team action.
"He's had a bit of time off and is still getting up to match fitness, he knows that himself and has admitted that himself," said the Stoke boss.
"Looking at him in training, he has got a lot to offer. He's really technical, so he certainly looks a little bit different offensively, and I think it's important we try and get him up to speed.
"We had a right good talk and he's been excellent. I know he's had some personal issues back home in Spain and I totally understand why he wasn't here.
"He's been really, really good. I know he's probably not match fit, but as regards him coming in here and doing his work, he's been very good.
"You watch him offensively in training and there's definitely something there."