Hello, I am a Lyon supporter and I wanted to give a bit of insight about Jake O'Brien.
First of all, he is an amazing character, hard working, never giving up. He scored crucial goals when everything seemed going to pot. He scored the winner for the first win of the season (after 12 games!) or a goal in the Cup final for instance.
About him being slow, that's non sense. He is one of the fastest players in a league where so many are more sprinters than actual football players. I never saw him being outrun by anyone. However, as it was said, as a giant CB, he needs time to turn and switch directions. But after the first two strides, he's unbeatable.
However, and this is highly debated here, many supporters (like myself) think he is a real liability defensively as his positioning can be diabolical. On some occasions, you can see him spinning two or three times on himself before finding his man. Despite his height, he is no monster defending the box. He let two of the small players of the league score headers against us. In the Prem, especially in a low block, I reckon that it could be a disaster.
He is okayish on the ball, no issue there. But it definitely should be considered in a back 3, not in a back 4.
The lad came as a weird Textor signing and established himself as a starter. There's a lot to love about him, and I really wish him well. The jump to the Premier League is a tremendous challenge. I don't think he's ready now, but he improved so much in such a short time here that I'm actually curious to see how it will turn out. I would say it's a 50/50 situation.