Liverpool defender Jon Flanagan must work on his "physical resistance" if he is to play regular first-team football, according to manager Jurgen Klopp.
Prior to his January comeback, Flanagan had spent 19 months on the sidelines due to a knee injury.
The 23-year-old, who has one England cap, last played for the Anfield club when he skippered his side at Southampton in March.
After featuring in the under-21 side's 2-1 victory against Norwich City on Monday, Klopp provided an update on the right-back's fitness,
"Flanno is in a situation that [means] he cannot train all the time," he told a news conference. "When you're out for this long period, you can't train all the time and you can't build a base, that's all.
"It's a little bit similar, different story, to what I said about Daniel Sturridge with the long injury breaks.
"If we want to help him, we need to work on his physical resistance so that he is ready for more than one game and then two or three days' recovery or something."
Since making his debut as an 18-year-old against Manchester City in April 2011, Flanagan has made 48 appearances for Liverpool in all competitions,
His best season came in 2013-14, when his 25 appearances earned him a place on Roy Hodgson's standby list for the 2014 World Cup.