Charlie Mulgrew left Celtic in the summer for Championship side Blackburn Rovers.
Celtic's Stuart Armstrong celebrates scoring their first goal
Charlie Mulgrew has suggested that former Celtic teammate Stuart Armstrong's form this season has come as no surprise to him, having seen how good the midfielder was in training before his departure last summer, the Evening Times reports.
Armstrong has arguably been the biggest beneficiary of Brendan Rodgers' arrival at Parkhead, having gone from a fringe player under his predecessor Ronny Deila to being a talisman and a player that some Hoops fans have suggested could be a future captain since he started working with the Northern Irishman.
But while some Bhoys supporters would not have imagined just how good Armstrong would become this term, Mulgrew - who joined Blackburn from Celtic last year - has insisted that the potential was always there.
"He has scored a lot of goals but to be fair, he always did well in training under the last manager," he said, as reported by the Evening Times.
Celtic's Stuart Armstrong and Erik Sviatchenko during training
"I could see his ability and Stuart has added goals to that, so fair play to him. He's a good addition to the squad.
"Under the last Celtic manager, I felt that he did well wherever he played. He helped us a lot, he's full of unselfish running and always worked hard."
There is no question that Armstrong is fully deserving of the call-up he has received to the Scotland squad ahead of their clashes with Canada and Slovenia, having been a key part of the Celtic squad that could wrap up the title in the first game back following the break.
The 24-year-old has scored 11 and contributed six assists in the Scottish Premiership. And while his partnership with Scott Brown in the middle of the park has been crucial to the Celtic's success, his versatility has also been highlighted under Rodgers.
And while some may have initially felt that Rodgers was one of the few people who saw something special in Armstrong, Mulgrew has argued that the talent was always evident to those who worked closely with him.