Jon Flanagan
Defender Jon Flanagan is out with a knee injury Reuters

Liverpool manager Brendan Rodgers has confirmed he will be without full-back Jon Flanagan for "a few months" as the injury he suffered during pre-season appeared to be worse than first thought.

The 21-year-old defender picked a knee injury against Preston North End in a friendly on 19 July.

Having being on the sidelines since then, two weeks ago the right-back claimed he was ready to return to action.

"I don't think it will be too long now and I think I should be back after the international break if all goes well," Flanagan said at the time.

But Rodgers claimed the young defender required an operation after suffering a set-back in his recovery.

"Young Jon Flanagan, unfortunately, has just had an operation that will probably have him out for a few months, which is disappointing," the manager said to Liverpool's official website.

Flanagan was a crucial player in the second half of Liverpool's season last term while covering long-term injuries to both Glen Johnson and Jose Enrique.

Nevertheless, Rodgers bolstered the full-back positions during the summer with Spanish duo Javier Manquillo and Alberto Moreno, so he has a few options to consider - and that includes Enrique and Johnson.

The manager confirmed England international Johnson is close to a return to action following his latest injury.

"Glen Johnson should be back training over the course of the weekend," Rodgers said.

Meanwhile, Rodgers was also positive about Daniel Sturridge and Martin Skrtel being on the road to recovery from their respective injuries, although he said it might take Joe Allen a bit longer to be viewed in the same position.

"Martin Skrtel is back training with the team, which is great news for us," he said. "Daniel Sturridge should hopefully be back training at some point next week. Joe Allen is still out and he'll be out for a few weeks yet."