Grogan to enter Lions' den
The London club will start as one of the pre-season favourites to win promotion from Division One, with manager Mark McGhee (pictured) having inherited a promising squad brimming with youngsters.
McGhee took Millwall into the Division One play-offs last season, where they suffered a heart-breaking last minute loss to Birmingham.
Grogan, a 21-year-old midfielder, has accepted a contract after impressing The Lions' coaching staff during a recent two-week trial.
Speaking to the official Millwall site, McGhee said: "Kevin is a different type of midfielder to those we have here in that he is a midfield playmaker and it would be nice to add someone like that to our squad.
"We tried to bring in someone like that last year with Stephen McPhail because I wanted that type of player. We couldn't afford him, but regardless of his time here, I think he is a great player.
"Kevin Grogan has a lot of quality, a lot of pedigree and is someone we could do with keeping here."
It is believed that Grogan will be initially offered a 12-month deal having been told he could leave Old Trafford last season as Sir Alex Ferguson continued his regeneration of the youth system.