But does the player's Ibrox appearance mean he is definitely a fan of Steven Gerrard's Rangers?
One of Celtic's rumoured transfer targets was pictured outside Ibrox last year draped in a Rangers scarf.
Rangers' Glasgow rivals, Celtic, have enquired about signing the Northern Ireland international, according to Teamtalk.
But the following image, tweeted via McNair's Instagram account in March 2018, is unlikely to make him popular in the east end of Scotland's second city.
View this post on Instagram
Should the versatile midfielder indeed join Celtic this summer - and it's claimed he could be sold if Middlesbrough can recoup the initial £3 million they paid for him a year ago - he would not be the first Rangers-affiliated player to be lured to the other side.
The former Celtic favourites, Davie Provan, Kenny Dalglish and Jock Stein are all reported to have grown up supporting the Gers.
Celtic fans - would you be bothered by McNair's apparent Rangers affection?
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