Leeds United are the "fittest team" in the Premier League, according to Manchester United boss Ole Gunnar Solskjaer, who says Marcelo Bielsa is "a coach with all the details".
United are currently preparing to take on their rivals in the top-flight for the first time in 16 years, with the Whites arriving at Old Trafford on Sunday afternoon.
Bielsa guided the Yorkshire club to promotion in 2019-20, and his team have made a huge impression since returning to English football's top tier.
Leeds are sitting 14th after their opening 13 fixtures of the current campaign, but have earned plenty of admirers with their energetic, attack-minded style of play which has garnered several impressive results.
The Whites' latest show of slick football in the final third came during their 5-2 win over Newcastle on Wednesday, and Solskjaer is wary of the threat Bielsa's men will pose his team this weekend.
“He’s done a great job with Leeds and he’s done a good job with many other teams as well," the Norwegian head coach told MUTV of the impact Bielsa has had at Leeds.
"You see that there’s so much going on and to analyse those games takes a bit of concentration and time. You can see he’s a coach with all the details and he’s got his teams running.
"They’re the highest running and sprinting team in the league, probably the fittest team, so that’s one of the battles that we have to stand up to. It’s going to be a physical game.”
Solskjaer added: “They’ve had I don’t know how many games with over 25 shots and they create chances. They go forward, it’s a good team to watch and as you said the games are entertaining.
"Then again, for us, this is about three points and standing up to the problems they cause us. You’ve got to solve those problems and give them problems yourself as well.”
United and Leeds had many memorable battles during Solskjaer's playing days, with the 47-year-old grabbing a brace during a 4-3 win for Sir Alex Ferguson's side at Elland Road in 2003-04.
“That was a good game for me. I remember those two goals fondly," he said. "I enjoyed a goal at Old Trafford, I think I came on and we were 1-0 down and I get over Ian Harte [at the] back post and headed it back down to the other post.
"That was a good moment for me as well. It was a good rivalry, it was a fierce rivalry. Of course, they were flying high, they had a very good team and did well in the Champions League, so the games were high level, good quality and we knew that they were important games for us to be able to win the league."