Liverpool manager Brendan Rodgers has said Martin Kelly still has some way to go in his recovery from a cruciate knee injury.
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When first-choice right-back Glen Johnson was ruled out of Saturday's 2-0 defeat to Arsenal, Rodgers overlooked the 23-year-old and instead gave Jon Flanagan his first Premier League start.
He said that was because Kelly felt he had struggled the previous week against Crystal Palace, when he came off the bench to play his first league game for 13 months.
The England international's only other appearance this season came in September's Capital One Cup defeat to Manchester United.
And Rodgers told Liverpool's official website: "Just getting him fit is the most important element of Martin's career at the moment.
"I gave him a little sample in the game against Crystal Palace, 30 minutes when I felt we had control of the game, and afterwards he didn't feel quite right which is why young Jon Flanagan played the Arsenal game. It is going to take time for him.
"He is playing in the under-21 games to get his fitness up. Martin is working very hard and we are trying to give him as much game time as we can outside the first team so when he goes in he can contribute without worrying if he is going to break down.
"When you have been out for so long, naturally you are a wee bit tentative. When he played against Palace it was his first Premier League appearance for 13 months, so naturally it is going to affect you in some way."
Rodgers stressed that he remains an admirer of Kelly, who featured regularly at right-back at the start of his reign but is regarded by many as a future centre-back.
The Northern Irishman said: "He is a multi-functional player, he can play in both positions well and it may well be centre-half is his best position.
"He was excellent when I first came here last year, started the season well, was one of our best players and was unfortunate he picked up the injury.
"But as time goes on and as he trains more and gets more games in the under-21s you will see him get back to where he was, which was [at] a high level."