Steve McClaren believes that Cristiano Ronaldo's return to the club will either 'make or break' Manchester United manager Ole Gunnar Solskjaer.
United have lacked consistency this season, with Solskjaer receiving a considerable amount of criticism from pundits and supporters following recent results, which have a 2-0 loss to Liverpool and a 5-0 defeat to Manchester City.
Former England boss McClaren was assistant manager to Sir Alex Ferguson when United won the treble in 1999.
Ronaldo, who enjoyed an impressive spell at United between 2003 and 2009, returned to Old Trafford at the end of the summer transfer window as he left Juventus.