Former Scotland international Michael Stewart thinks that Gary Mackay-Steven struggled at Celtic due to his fragile confidence and the fact he was not a main man at Parkhead.
The 27-year-old was signed by Celtic from Dundee United in the 2015 January transfer window, but failed to make his mark at the Scottish champions and was sold to Aberdeen this summer.
Mackay-Steven has found himself hitting form under Derek McInnes at Pittodrie and a number of Celtic fans have been reassessing why it did not work out for the winger at Parkhead.
For Stewart, the reason for the failure is confidence related, with the wide-man "fragile".
He explained on BBC Sportscene Extra: "I think he is a fragile player.
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"Confidence is a huge part of his game and competition is so stiff at Celtic, they are a massive club.
"He probably needs to feel like he's one of the main guys in the team", Stewart added.
Mackay-Steven has made 19 appearances across all competitions for Aberdeen in the current campaign, scoring five goals and providing his team-mates with three assists.
The winger hammered home a hat-trick at the weekend as Aberdeen crushed Hibernian 4-1 at Pittodrie.
