Mikel Arteta first became aware of the job Chris Wilder was doing at Sheffield United when they were still in the Championship.
Having been told about their tactical innovation, our manager - then a coach at Manchester City - studied the Blades in depth, and liked what he saw.
"Incredible," he said. "I start to analyse his team two years to understand some of the things he was doing and I think him and the coaching staff have done a really, really good job.
"Not just for the way the play because it is a very clear style, but for the culture they have created around the club and this feeling that you can sense around the team and how they compete. I think it is remarkable what they have done.
"I was told by someone that we had to have a look at them, and I always like to see different trends, different ways of playing, formations, structures, patterns, and I was impressed with some of the things they were doing. It is always good to have this information."
We host the Blades at Emirates Stadium on Sunday, and Arteta is expecting a major challenge despite the visitors' struggles so far this season.
"The margins in the league of winning, drawing and losing are really small and the details are crucial, but they have generated big chances every game and they've been really unlucky in my opinion not to get anything out of those games," he said.
"We have experience of playing against them both in the Premier League and in the FA Cup so we know how difficult it is to play against them.
"The season they had, the way they have evolved as a team since they joined the Premier League has been unbelievable, the work that the manager has done with the coaching staff with the resources they have is remarkable. We need to be really alert and we have to play at our best again."
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