Every time I'm about to write about the fringes of the Spurs roster, I'm reminded of how good we have it. With Boris Diaw playing at such a high level, the Spurs already have three above-average bigs in their rotation and with Leonard almost certainly spending some time at power forward in the playoffs, that's all they need. But the regular season is long and the Spurs will need their depth to fight for seeding in the Western Conference.

Early in the season, Pop anointed Jeff Ayres as the team's fourth big, but lately the play of Aron Baynes has garnered some much-deserved attention. Baynes scored and rebounded well in the last two games in which he received substantial minutes, while Ayres looked over-matched as a starter with Tiago Splitter out and didn't look much better as a reserve against the Clippers. So let's take a closer look and see who brings more to the table.

The case for Baynes

Baynes extended his minutes in his last two games, and he responded with two great performances. Bearing in mind that the competition was lower-tier -- Toronto and Utah -- and that those were outlier performances, Baynes scored 14 and nine points respectively and did a fantastic job on the boards. If he can come in and provide his brand of physicality on the offensive boards and contribute some easy points off pick-and-rolls and put-backs, then the Spurs have the right complement for Diaw, at least on the offensive end.

Baynes lacks range (1-16 outside five feet) but so does Splitter and he still contributes greatly to the Spurs' success by being a good dive man off pick-and-rolls. So there's no reason why Baynes, who is a good finisher, can't do the same. Baynes' screens are wide and he seems to have very good hands for a guy of his size. And that's all you need when sharing the court with fabulous passers like Ginobili, Belinelli and Diaw.

The case against Baynes

Baynes seems like a good running mate for Boris Diaw but can he play next to Splitter or Duncan? Bangers is not exactly the quickest of guys and he's regularly torched by mid-range shooters since he can't drop and recover on the pick-and-roll. The Spurs live with that when Duncan does it because he provides a great deterrent as an elite rim protector. But Baynes has not proved to be an above average defensive player in any setting yet.

When Baynes shares the court with Splitter, the offense suffers because neither has a serviceable jumper, which causes spacing issues as the defense plays off them, packing the paint. Those can be overcome by good cutting and passing, but both guys work better screening than they do on the move. Baynes is essentially the third Spurs center, which is why he didn't see playing time against the Clippers. By fitting poorly next to Duncan and Splitter, Baynes can't augment the Spurs lineup flexibility in the slightest.

The case for Ayres

If Ayres looks over-matched as a starter, it's only because he's simply not yet starting material. Jeff joined the team this season, so it's no surprise that he's occasionally lost on the court. We shouldn't put too much weight on the play of a guy that is not ready to start, and yet is thrown into the fire in his third month in a system with a famously steep learning curve.

Ayres is mobile enough on defense to handle perimeter-oriented power forwards. Unlike Baynes, he does a good job contesting jumpers, which is something the Spurs are asking of every big whose initials aren't 'TD'. That mobility also allows him to show on pick-and-rolls and recover, which is a nice tool to have. The Spurs often choose to have their bigs drop, but the PFs are regularly required to hedge and Jeff does that just fine. He is not a good rim protector but he is an exceptional rebounder, which means that in theory he is versatile enough to be able to play with all three of Duncan, Splitter and Diaw.

Finally, an underrated skill for a big is running the floor and Ayres does a fantastic job of it. It might not result in points for him, but by racing down the court and sucking the defense in, Ayres opens up secondary break opportunities for the three point shooters. Add his work on the offensive glass and you have a solid complementary big.

The case against Ayres

Pretty much everything that has to do with offense -- besides rebounding and running the floor -- has confounded Ayres. He screens inconsistently, sometimes making great contact and others barely grazing the opponent. He often fumbles passes that pretty much every other Spurs big snags with ease. And when he does catch the ball, he averages a terrible 56% on his shots at the rim. He was used as a pick and pop big at Indiana, but the Spurs don't seem interested in using him that way at all, which is not surprising since he is shooting 23% from outside five feet. He is not a particularly good passer, either.

If he was a game-changer on defense, then you live with the offensive limitations. But despite having some intriguing physical tools, he doesn't seem to be anything close to that. Teams get to the rim more often when Ayres is on the court and score at a higher level than when he is on the bench. Now Baynes is not much better, but the Aussie seems to have more room from improvement simply by playing within his limitations. Ayres sometimes overrates his mobility and tries to do too much, resulting in errors like hedging hard and leaving Kevin Love open or waiting an extra second before rotating.

Verdict

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Jeff Ayres seem to be the better fit for the roster, at least on paper. And the fact that Baynes is still eligible to be sent down to the Toros means that he could continue to develop while Ayres gets some much needed reps with the team. But Ayres play has been very erratic as of late while Baynes seems to be ready to get minutes now. It's possible that easing Ayres into things on limited minutes could be exactly what he needs to get his comfort level to the place it needs to be.

There's also the question of their contracts. While the Spurs will have Ayres under contract next season, Baynes will enter restricted free agency. It would benefit the front office greatly to have a larger sample size to form an idea as to how good Baynes actually is when it comes down to decide whether to keep him or not.

I'm a big proponent of using depth to gain advantages through match up adjustments so I still believe there will be games where Ayres and Bonner will be the better options and the Spurs should not hesitate to play them over Baynes. Let's not mince words: Baynes is way too slow to play power forward in the NBA. But if the Spurs are looking for someone to give them 10-15 minutes a game at center next to Diaw, the Aussie seems to be the better alternative, at least for now.