Yeah, Marion's been playing like garbage recently. Not that I'm complaining--he was nails for an entire month before that.
Anyway, Bowen + refs gives a lot of players trouble. If you think the Suns have it bad, imagine how the Nuggets must feel--Bowen shuts down Carmelo Anthony, too, and Melo is the Nuggets' only legit offensive threat.
The Suns actually have a couple of options. First, they can go small, and because Quentin Richardson isn't available to absorb mismatches, Marion will wind up matched against Horry or Mohammad and have his usual success. Or, if the Suns' bigs are healthy, they can play the Spurs straight up, absorb the loss of Marion's points, and get those points back at other positions.
In the last game, Bowen switched over to Boris Diaw for a time--he was still effective, but had less success than he usually does against Marion. My thought is that the Spurs will try to use Bowen as a "fireman" this time around, switching him from Sun to Sun as this or that player heats up.
The good news is that Bowen can't guard Steve Nash (and he might not be able to guard Barbosa, either). Nash can guard Bowen just fine, though.