PER Diem: Feb. 18, 2009

The ongoing saga of Tracy McGrady took another bizarre twist yesterday, when he told our Stephen A. Smith that he would undergo microfracture surgery on his left knee and miss the rest of the season. This was unexpected given that a week ago the team announced an MRI on his knee showed no change, and that McGrady proclaimed himself ready to play out the rest of the season.

But for the Rockets, it may at least offer some clarity to an unsettled situation that had the team not knowing until minutes before tip-off whether T-Mac would be playing -- and not knowing until several minutes after tip-off which T-Mac was showing up.

As a result of his up-and-down season, the Rockets' performance hasn't been much different whether he's in the lineup or out of it. In fact, Houston is 13-6 when McGrady sits out and just 20-15 when he plays.

Those splits are more dramatic when you pair them side by side with another Rocket, Shane Battier. Houston is 20-12 when Battier plays, and 13-9 when he sits out.

Superimpose the two and you get the following:

With Battier, without McGrady: 12-3
With McGrady, without Battier: 12-7
With both: 8-9
Without both: 1-2

Weirdly, Houston has played its worst when both are present -- leading into the break, the Rockets lost to Memphis, Milwaukee and New York with those two in the lineup. However, that may be because McGrady's condition appears to have only worsened as the season has gone on. Battier missed the season's first month, when McGrady played his least-awful basketball of the season, and Houston went 10-5 in that stretch.

Take October and November off the table, and since Dec. 1 the comparison looks more like this:

With McGrady: 10-10
Without McGrady: 12-4

As a result, it's hard to get too worked up about the loss of McGrady doing much damage to Houston's playoff hopes. The rest of the team is as healthy as it has been all season, and as the Rockets showed during their 22-game win streak a year ago, they have more than enough depth to shrug off injuries to their front-line talent.

Houston will most likely still make the playoffs, and might even win a round when it gets there -- which would be rather ironic given T-Mac's tortured first-round history.

But this injury does have two serious impacts. First, on the trade front, it takes the option of dealing him off the table. Houston had been sniffing around Vince Carter, but even in the Nets' dire financial state I don't think they can stomach dealing for a player who may never play a game for them (McGrady's contract expires in 2010, and if he goes the microfracture route his recovery would last well into next season).

Second, and perhaps more importantly, it forces us to recalibrate Houston's ceiling. Though the Rockets didn't have their lineup healthy all season, there was always the thought in the back of our minds that a healthy McGrady-Yao-Artest trio paired with Houston's bench could be a real threat come playoff time.

Now? It's just not as scary a proposition. The Artest-Battier-Yao squad has a nice nucleus, and it's possible Houston will add to it in the next 48 hours. But I think we can scratch one team off our list of potential Western Conference champions.

John Hollinger writes for ESPN Insider. To e-mail him, click here.