Tim Wakefield, Josh Beckett and Lester were the only dependable starters in the first half (John Smoltz, Daisuke Matsuzaka and Brad Penny all had losing records). While Lester remained effective in the second half, Beckett began to struggle, and when All-Star Tim Wakefield was placed on the disabled list, Buchholz replaced him in the rotation.
The first half of the season saw a lack of consistent starting pitching with only Wakefield, Beckett, and Lester performing well.  Lester continued to be effective while Beckett struggled, leading to a change in the rotation when Wakefield was injured.