The Red Devils are preparing to take on Spanish side Sevilla in the second leg of their Champions League last-16 clash at Old Trafford on Tuesday night.
Manchester United have improved under Jose Mourinho this season but not as quickly as Manchester City, who are a long way clear at the top of the table.
Eric Bailly’s injury problems and Victor Lindelof’s struggles following his summer move have led Mourinho to rely on Jones and Smalling.
The former Blackburn Rovers defender arrived at Old Trafford in 2009 as a promising teenager under Sir Alex Ferguson, while Smalling moved to Manchester United from Fulham eight years ago.
However, both of the England internationals have struggled to realise their talent at the 20-time English champions despite their undoubted promise when Ferguson signed the defensive duo.
Vidic was team-mates with the centre-half duo during the latter stages of his Manchester United career before he moved to Inter Milan in 2014.
However, the Manchester United legend appeared to accept some of the blame of Jones and Smalling’s lack of progress.
“As a forward you react to what your opponent does,” Vidic told the Daily Express.
“If as a defender you lose that belief and think: ‘Should I be here, or here, or be here, then it’s difficult to play. So that didn’t help them.
“If they had done something bad I could have said: ‘Okay, he’s 24 but where was I to help him?’”
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