Kelly's main aim now is to get as many minutes under his belt as possible as he targets a return to his best form in order to challenge for a first-team place.
"It was good to get the first 90 minutes under my belt after so long," Kelly told Liverpoolfc.com.
"I played last week in a behind closed doors friendly but to get 90 minutes for the U21s was superb for me and my fitness.
"I just want to get as many games in as I can. I missed so much last season and it's difficult mentally coming back from 11 months out and knowing you are not where you were last pre-season, because I started the last pre-season flying and that's where I want to get back to."
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