The other has only played in the Dutch League and we overpaid by £15m at least.
Ajax in the CL last season, 100% wins in group stage:
4-2 and 1-5 wins against Sporting CP
4-0 and 1-3 wins against Borussia Dortmund
2-0 and 1-2 wins against Beşiktaş
Now, I will concede he was also involved in the 2-2 draw and 1-0 loss to Benfica, so not flawless. But to come out 100% wins in group stage including 7-1 aggregate playing against Dortmund let alone the others in the group is nothing to dismiss.
Not saying Martinez will be a world beater but to say he has only played in the Dutch League is a bit of an unfair dismissal. Suarez played in the same Dutch league before he took a bite out of the Premier League.