Did he do that much of any amazing job at Derby? They finished 6th which was the same as the season before, similar in the way of points and goals scored while conceding more.
Even at Chelsea I think it gets over hyped a bit. They won Europa League the season before he came in and finshed 3rd. He finished 4th with fewer points having conceded a lot more but in fairness scoring a lot more too. They also got knocked out in the last 16 of the Champions League losing 7 - 1 on aggregate.
That doesn't mean he can't be a success with us and I think it's worth a go but then I would say the same with Knutsen. He has managed to take a team that has never won the top league potentially back to back titles while only losing 4 games over 2 seasons. They also managed to draw 2-2 and win 6-1 against Roma which isn't bad.