I'd like it.
1) Blair has the highest ceiling of any bigman on the team outside of TD. Yes, Splitter should be good but Blair's ceiling is higher. He's not too likely to reach his ceiling due to his knees and his height ... but the Spurs might as well begin the season with him in the starting lineup to gauge his progress.
2) It guarantees Blair a healthy amount of minutes. With Splitter, Bonner and McDyess splitting minutes next to Duncan, Blair could hypothetically get lost in the shuffle if he's coming off the bench. Starting Blair forces Pop to keep him involved.
3) McDyess doesn't begin trying until the All-Star break ... so there's no reason to waste starts on him early on. Bonner shouldn't start, period.
4) It keeps the pressure off of Splitter. Early in his Euroleague career, the pressure would get to him and he had a tendency to meltdown late in games. In this transition to the NBA, there's no guarantee that he'll react well to pressure in the NBA. Building up his confidence slowly is the way to go.
5) Splitter could fit better off the bench anyways. With his Spanish team, they ran pick-and-rolls with him a ton. They also posted him up a ton. With Duncan on the court, Splitter wouldn't get those opportunities. Off the bench, he could anchor the reserve unit. Plus, having one of Duncan or Splitter on the court at all times gives the team a bigman who can defend centers on one end and key the offense with passing on the other end.

@ Blair in the starting lineup to begin the season.