He can't be much slower than Barry can he? Carrick? Pirlo? Alonso? I'm by no means saying he's as good as those, but pace is only one attribute. Positional intelligence is as if not more important in a Pep team.
Centre half wise, Lescott was a slow as they come, Terry & Vidic would both be considered carthorses.
Having seen BVB, Bayern and Mönchengladbach in the flesh, I'd say the German league is arguably quicker than the Prem.
The transitional play of the German sides is incredibly quick.
Fair comments, but ones that should perhaps come with a few provisos.
1. Barry, Pirlo, Carrick et al, all played as defensive midfielders, a less vulnerable position than centre half. I know Martinez can fill both of those roles, but of the two it's the centre half that concerns me most. That notwithstanding, Martinez is slower than all of those players. He's Nolito with a pebble in his shoe slow.
2. Lescott was indeed as slow as they come. When he played under Mancini he was fine, sitting relatively deep with Nige and Gaz Baz in front of him. As soon as Pellegrini came along with a far higher defensive line and less cover, he looked like a rabbit in the headlights and his days were numbered. Martinez is far more technically accomplished than Lescott, but the concerns would still be legitimate IMO.
3. The transitional play in German football may or may not be quicker than the EPL, but the overall tempo in the EPL is surely higher. Less time to think, less time to dwell on the ball, less time to adjust. Plus, it's hard to judge anyone coming from Bayern. Their dominance of that league, and associated reduced pressure on their defensive players, is near total.
4. Positional intelligence may or may not be more important than pace in a Pep team, but there are other factors that hold sway in the EPL as well in terms of defensive effectiveness, one of which is physicality. The hoof downfield to either a gigantic donkey or an electric hare in acres of space was a constant opposition gambit last season, as they adjusted to our monopolisation of possession pretty quickly, particularly at the Etihad where we were held, what, 8 times? Even Stones, who's a decent size, struggled with it at times, and I lost count of the number of times Otamendi, Kolarov and Clichy got either scorched for pace or simply outmuscled. Even after Kompany returned to the fray we still had trouble dealing with it. Leicester and the rags both noticeably kept Vardy and Rashford out towards our left flank (ie. well away from Kompers) for all goalkicks and long clearances. How would Martinez fare in such circumstances? He's always struck me as an elegant player and not an all-in wrestler, but I think in the Prem it helps to be both. A lack of pace in isolation might be overcome; a lack of pace and brute force might not.
5. I think Zin said in another post that we will not operate with such a high defensive line next season, and you have additionally rightly pointed out that we are attempting to purchase defensive power and pace in the shape of Walker and Mendy. My concern as it was at the start of last season, and I was broadly right about it, is that whilst we might aspire to play a certain way, opposition teams in England will frequently adjust very quickly and exploit any perceived weakness. Within 8 weeks of the start of last season, the parked bus and the quick punt over our midfield, rendered our press largely redundant at a stroke and Pep acknowledged as such. I don't see that changing next season. Indeed with the addition of Bernardo Silva and (hopefully) Alexis Sanchez I see it getting more acute. We might want to draw teams out so we can have Sane, Jesus and Kun crucify them for pace in behind, but whether they'll be so obliging is another matter and I suspect we'll defend just as high next season as we did last.
6. As a simple summation, I'd be delighted to acquire the services of Martinez if it were all about what he does with the ball. Stones, Otamendi and Kolarov I thought were all excellent at bringing the ball out from the back last season and kick starting moves. From a defensive point of view however, I'm not convinced he wouldn't face the exact same difficulties as they did in terms of defending one on one against power and pace. If we're picking him up cheap (and we might given his age - nearly 29 - and his injury record) and we're going to rotate him with Ya Ya in the pivot role, then fine. He is when all's said and done a class player. If we're buying him as cover for centre half then I don't really see the benefit. I'd rather go all in for Bonnucci or Van Dyke