Mumba has returned to Norwich City after starting just seven Championship matches for Posh and only two following the arrival of McCann late in February. Mumba (20) scored the winning goal on his debut against Bristol Rovers in an FA Cup tie in January.
Coulson is back at Middlesbrough after starting five Chamoionship matches for Posh, but only one for McCann, the 3-0 defeat Huddersfield on March 4. On-loan midfielder Reece Brown, who is out of contract at parent club Huddersfield at the end of the season, remains at Posh, but will not be involved at Millwall. He was given the option of returning to Huddersfield
McCann wants to use players who are likely to at Posh next season so youngsters Andrew Oluwabori and Janos Bodnar will travel with the squad to Millwall tomorrow. Oluwabori is a forward who was released by Huddersfield earlier this season while Hungarian Bodnar, a full-back, is a member of the Posh youth team.
Striker Ricky-Jade Jones and wing-back Joe Ward are fit to travel to the Den.
"I want to look at players who will be with us next season,” McCann said. “It’s nothing against Bali or Hayden who are both great lads, but it’s only fair I gave them the option to go back.
"Andrew and Janos have impressed us since we came to the club so they will be in and around the squad at Millwall after playing for the under 23s today.
"We want to finish the season strongly, and we will need to be good tomorrow, but I also want us to enjoy it. Millwall still have a play-off place to play for and they are full of good, experienced Championship players.”
Millwall could effectively be out of the play-off race if Sheffield United win at QPR tonight (Friday). That would put the Blades six points clear of Millwall who have two games to play and an inferior goal difference.