Callum McGregor has laid out a challenge to his Celtic teammates after the win over St Mirren as Matt O’Riley looks to seal his move to Brighton this weekend. The Celtic captain was on the scoresheet once again as Brendan Rodgers’ team coasted to a 3-0 win over the Paisley club. With a two-point lead at the top of the Scottish Premiership restored, Celtic face Rangers next and it is likely to be without O’Riley as he puts the finishing touches on his big move to Brighton this weekend. And whilst the Dane does that, McGregor has laid out a challenge to his Celtic teammates after the win over St…