The Czech striker could be back "in a couple of weeks", according to his manager.
Aston Villa FC (@AVFCOfficial) March 12, 2015
The 25-year-old Czech striker suffered a serious leg break during a training session in January last season and has since been battling to make his comeback.
Things looked good for an October return alongside Christian Benteke, but complications in the healing process forced him to go under the knife for a second time, with the since-departed Paul Lambert declaring the whole ordeal a "nightmare" at the time.
He has since made considerable progress, however, moving up from non-contact work to training with the Under-21s, and has now re-joined his senior teammates.
Sherwood has been delighted with the dedication the tall front man has shown since his arrival at Villa Park last month, and believes he’ll soon be like “a new signing” for the club.
"Libor is back training with the group with contact,” he said. "He looks very good. He's making progress.
"Hopefully in another couple of weeks he will be like a new signing for us.
"He needs more time with the group with contact to build the confidence in that leg. It was a nasty injury. But he's certainly one who's impressed me."
Signed from Lazio in September 2013 for €6.5 million, Kozak netted four times in his first 15 games for Villa before suffering the leg break, and his strong presence up top could be a major boost to the club’s survival hopes if he can return for the final run in.
The eight-time capped international told Villa's official website on a potential comeback last month: "Every member of the squad has come up to me and given me words of support.
“The fans have been unbelievable too. They have been waiting for me! They keep asking me on social media - when are you back?
"I want to pay back this faith in me with some good performances and good goals. The fans here are so nice to me. What a feeling it will be to put the Villa shirt on again.”