We could adopt a '2 games on, 1 game off' rotation for the 3 CBs throughout the season?
Game 1: Koscielny - Mertesacker
Game 2: Koscielny - Vermaelen
Game 3: Vermaelen - Mertesacker
If everyone stays fit, then they'd probably get 30-40 games each following that system, and should stay nice and rested?