Derby County have loaned defender Scott Malone to Millwall on a season-long deal, while Mason Bennett has returned to the Den on a permanent basis.
Malone, 29, re-joins the Lions having scored five goals in 71 games for the club before joining Cardiff in 2015.
Forward Bennett, 24, scored two goals in nine games on loan at Derby’s fellow Championship side last season.
He leaves the Rams for an undisclosed fee having scored six goals in 90 games and remains their youngest debutant.
Bennett made his debut aged just 15 years and 99 days when he played against Middlesbrough in October 2011.
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