The Red Devils eased to a narrow win over the defending Premier League champions thanks to goals from Romelu Lukaku and Jesse Lingard at Old Trafford.
Chelsea FC squandered the lead against both Barcelona and Manchester United after Willian broke the deadlock in the Champions League and Premier League clashes.
The Premier League title holders dropped down to fifth place in the table and two points behind Tottenham Hotspur in the race to secure a place in Europe’s premier club competition.
Chelsea FC have only managed to win four of their last 14 games in all competitions to heap pressure on manager Antonio Conte heading into the final months of the 2017-18 season.
Former Blues winger Nevin is confident that Chelsea FC are improving under Conte despite some mixed results over the past few weeks.
“Chelsea played well in both games, except for Willian who played brilliantly,” Nevin told Chelsea’s website. “Since Christmas there has been a 5-0 win, two 4-0s, two 3-0s and nine clean sheets.
“The performances have been steadily improving of late, so the problem is not the last two games or the general form but the two aberrations against Watford and Bournemouth.
“Against United away you can drop points in any season, but to slip up in such an un-Chelsea like fashion has been the real cause of us falling out of the top four.”
Chelsea FC won the Premier League title with two games to spare last term after the Blues finished seven points clear second-placed Tottenham Hotspur.
The Blues will make the return trip to Barcelona for the second leg of their Champions League last-16 clash on 13 March.
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