Who cares about career numbers, though? This is a "what have you done for me lately" league.
Regular season stats the past two seasons:
Starbury:
2007-08: 24 games played, 13.9 ppg, 41.9% FG%, 2.5 rpg, 4.7 apg, 0.9 spg, 2.0 tpg
2008-09: 23 games played, 3.8 ppg, 34.2% FG%, 1.2 rpg, 3.3 apg, 0.4 spg, 1.6 tpg
Rondo:
2008: 77 games played, 10.6 ppg, 49.2% FG%, 4.2 rpg, 5.1 apg, 1.7 spg, 1.9 tpg
2009: 80 games played, 11.9 apg, 50.5% FG%, 5.3 rpg, 8.2 apg, 1.9 spg, 2.6 tpg
Playoff stats the past two seasons:
Starbury:
2008: DNP
2009: 3.7 ppg, 30.3% FG%, 0.9 rpg, 1.8 apg, 0.07 spg, 0.8 tpg
Rondo:
2008: 10.2 ppg, 40.7% FG%, 4.1 rpg, 6.6 apg, 1.7 spg, 1.8 tpg
2009: 16.9 ppg, 41.7% FG%, 9.7 rpg, 9.8 apg, 2.5 spg, 2.7 tpg
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Rondo has simply been a significantly better player than Starbury recently. I can't imagine that Starbury would be made a starter under any circumstances barring injury.