The 21-year-old managed a total of 28 appearances, including 20 starts, and bagged three goals last term, a steady increase on his involvement in 2011/12.
Leonard was switched from right-back to central midfield and he is happy to perform there for boss Phil Brown next season, in a campaign in which he is determined to establish himself as an integral part of Southend's starting XI.
"I'm over all my injury worries, I had a few during last season that cost me a few more appearances, but I was pleased to be involved as much as I was," he told the club's official website.
"I turned 21 last week and I've got another good season under my belt so I'm confident I can really push for a regular spot in the first-team next season.
"Obviously I joined initially as a right-back but was played in central midfield by the new manager towards the end of the season and I enjoyed playing there.
"He's seen me play at right-back in a couple of friendlies and in training games so he knows I'm happy to play there if needed.
"If I stay in central midfield I'd like to get a few more goals. I got three this season put I'd like to be pushing for eight to 10 as well as chipping in with some more assists."
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