Barcelona s head coach Xavi Hernandez . AP
The former Ajax coach took over at Old Trafford last summer after the team finished sixth in the Premier League, and this season they are third, with one defeat in the last 17 games across all competitions.
Man United have not lifted a trophy since winning the Europa League in 2017 but under Ten Hag they seem on course to return to football's elite.
"Ten Hag is a great coach," Xavi told reporters Wednesday. "Turning around Man United's situation was not easy and he is doing it.
"They are a very tough opponent tomorrow and he is a very interesting coach for me. He changes things up, the pivot can move, a lot of players join the attack, he's an attacking coach.
"He's a reference point for coaches that like this type of football."
Barcelona are in superb form themselves, having gone 16 matches unbeaten across all competitions, winning the Spanish Super Cup in January and stretching their La Liga lead to 11 points.
Xavi thinks the match-up, albeit in the Europa League play-off round, is mouthwatering.
"It is a spectacular game for fans, the two teams are arriving at their best moment of form in the season," said Xavi.
"Ten Hag has changed the face of their team. They have a lot of tools. It will be a game with a lot of intensity, Premier League teams are very physical.
"They are a top level European opponent, it's a great game."
Manchester United forward Marcus Rashford is one of the visitors' key weapons and has scored 13 goals in his last 15 games in all competitions.
The England forward has hit the best form of his career under Ten Hag.
"He's very fast, has very good dribbling, (can go) one-on-one, in transition he's very dangerous," warned Xavi.
"We need to take care of all of them but Rashford is one of the most dangerous players in Europe."
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