CELTIC legend Pat Bonner insists Hoops starlet Calvin Miller must bulk up to cement his place in the Parkhead first-team. 

Miller, 18, made his first start for the Glasgow giants on Wednesday night, playing just over an hour in an unfamiliar left-back role in the 1-0 win over Partick Thistle. 

He earned a rave review from boss Brendan Rodgers, with the former Liverpool manager comparing the talented teenager to England international Ryan Bertrand, who he coached in Chelsea’s youth setup.

Bonner said: “Brendan wanted to bring some different players in, so he has brought young Calvin Miller in there. 

Read more: Calvin Miller admits being nervous before his "perfect" Celtic debut

“It was a decent performance and he should be very proud that he was able to slot into this team and play. Brendan wouldn’t have put him in if he didn’t believe he had the ability to do something. 

“We have certainly seen his pace, however he is still a light, young player. 

“I think that does matter when you take a step up. I remember coming to Celtic and I was about 12 and a half stone, and by the time my career ended I was 14 and a half. 

“So you grow into it and become a man and I’m sure all of that will happen for that young man, so it is a great achievement for him. From Celtic’s point of view, Brendan has been able to change a few things and have a look at some new options.”