The Red Devils have responded following a difficult start to the Premier League season under Jose Mourinho to record successive victories.
Manchester United were 2-0 winners at Burnley before the international break to ease the growing pressure on the Red Devils manager.
The 20-time English champions ended Watford’s perfect start to the season with a 2-1 victory over the Hornets at Vicarage Road.
Manchester United will take on Swiss side Young Boys at Old Trafford on Wednesday in the first ever meeting between the two European clubs.
Mata, who was part of the Chelsea FC team that won the Champions League in 2012, warned against complacency ahead of the start of their European campaign.
“We start away against Young Boys, which is a big incentive for many of us in the dressing room who are yet to play against them,” Mata wrote on his blog One Hour Behind.
“It would be a huge mistake to underestimate the Swiss side just because they aren’t as big of a name as other teams, with many of those huge clubs also featuring in our group.
“Young Boys won their league last season by a considerable margin and they have started this campaign by winning all of their matches, including those in cup competitions. We are talking about a team that is in great form and will be facing us hugely motivated, just as every opponent does when they play against Manchester United. It will be a tough start to the Champions League.”
Manchester United face Young Boy’s domestic rivals Basel in the Champions League group stage last season.
The Red Devils were 3-0 winners against Basel in their Champions League opener at Old Trafford back in September 2017.
Manchester United suffered a 1-0 loss to the Swiss outfit in the return fixture in Switzerland.
Mourinho has won the Champions League with FC Porto and Inter Milan but fell short with Real Madrid, Chelsea FC and Manchester United so far.
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