The manager told the club's website: "It's been really difficult for Glen because he has wanted to give so much more.
"He has wanted to put himself out on the training pitch every day and play games but he was nowhere near 100% right. Of course when you put yourself out there you are getting judged.
"We needed to come together to find a way to get him back to his best. That meant taking him out in order for him to get back to that level. Now he's feeling fresh and playing for the first time in ages without any injuries. Now you see that mobility and running power that he has."
Liverpool face Sunderland in the Premier League tomorrow.