Well they are all the same age, but you can't really put Dero's conditioning in the same bracket as Koevermans and Frings. As someone aptly pointed out in the past, he's played far less total games in his career than Frings and is probably carrying less wear-and-tear.
Sure we need better players to surround our stars, but an apples-for-apples who's the designated player you want on your team? I'll take Dero. Comparatively he plays more games and has more of an impact than either of the alternatives.