The Spurs were the big 4 during the 03, 05 and 07 le runs. Bowen seldom missed games, but when he did, the Spurs didn't look the same. It's not surprise the defense fell off the cliff once Bowen lost a step. At the time, Pop and RC thought they were to replace Bowen with a SF that, while inferior on defense, has offensive game too. It was supoused to be RJ. But the experiment failed miserably. Btw, the only players that didn't have problems with Bowen's defense were Dirk and 'Melo. Dirk was too tall and 'Melo too quick and strong.
The Spurs returned to elite with the addition of Green, Kawhi and Diaw, since then the traditional Spurs defense recovered.