Let's just be clear about this. It is incredibly rare for a 5-man rotation to stay intact for an entire season. Remember last season when we had a big pile of quality starters(Dice, Penny, Smoltz, Masterson, Wake, Lester, Beckett, Buchholz), yet only ended up getting consistency from Beckett and Lester? Wakefield is still an important part of the starting rotation, even as a #6 starter. Someone has the flu? call Wake. Minor injuries like a torn fingernail or sore hamstring? call Wake. Daisuke being Daisuke? Someone has a rough start? Warm up Wake. He's a good pitcher that can pitch as a starter or long relief.
I can't say this enough times, but by having a quality veteran guy waiting in the wings, it means they don't have to rush guys up like Bowden/Tazawa, etc, that could use a little bit more time in the minor leagues. Wakefield wants a shot at the Red Sox wins leader, and between spot starts and long relief, he can still get the 9 a year he needs. Its a good situation, and management knows it, especially since they cut the costs on his rolling contract this year. Wakefield is a win-win situation, and they will not trade him.