The Posh spent the majority of the summer looking to add to their defensive ranks as they bid to make an immediate return to the Championship.
A deal was finally reached in the final hours of the window as Watts secured the third loan of his career by agreeing to spend the first half of the season at London Road.
However, McCann will face a wait to field his new temporary addition as the versatile defender continues his battle back from an injury suffered during Newcastle’s pre-season trip to Austria.
Watts is expected to return to contention over the next month and McCann is looking forward to seeing what the Magpies defender can offer his side.
He told the Peterborough Telegraph: “There are not many left-sided centre halves around. We had options on the table but we believed Kelland was the one we could wait on. He’s really aggressive, dominant in the air, can control the ball, quick and is mobile.
“He’ll be in and around the group and he’ll be following a plan to get him fit. He’ll be here a couple of days a week, at Newcastle a couple of days a week but he wants to be at the games.
“During the first few weeks, we need to get him to understand what we’re about as a club and get to know everyone. He’s used to playing a similar style to ours at Wigan and Plymouth and he’s a great signing for us when he gets fit.”
Watts was not the only United academy product to secure a loan switch on deadline day at Matty Longstaff and Lucas De Bolle made respective moves to Colchester United and Hamilton Academical.