The former Leeds United youth team captain, pictured, left the SW Jackson Utilities Stadium on Friday for a return to the professional ranks after going on trial at the Championship's Millers in recent weeks.
Lenighan is also well known to Rotherham manager Neil Redfearn from his time at Leeds United’s academy before his release at the end of the 2013-14 campaign when he joined Harrogate Town. He spent the latter part of last season on loan at Alfreton Town.
In a statement announcing his departure, officials said Rotherham made a formal approach for the non-contracted 21-year-old who made 22 appearances for the Premier Division club this season and scored one goal following his arrival in the summer from Harrogate Town.
A spokesman said: "All at the club wish him well on his return to professional football. The club also wish to thank Rotherham United who have agreed to play Frickley in a pre-season friendly ahead of the 2016-17 season."
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