Starsky Without His Hutch
When the Rockets finalized the trade that resulted in Tracy McGrady being added to their roster, their theory was most likely that by pairing McGrady with Yao Ming, they were done looking for their two franchise players. That dream lasted for all of one season, the 2004-05 one. Since then, in the two most recent seasons including this one, both players have had their seasons ravaged by injury and have only played fifty-one games together. Ming has played in thirty-three contests without McGrady and McGrady has repaid the favor by competing in thirty games with Ming on the sidelines.
With Ming playing alongside McGrady, he has put up some very good numbers. He is averaging 23.1 points per game with a 61.1% true shooting percentage. But without McGrady, Ming has looked like anything but someone an NBA team should be building around. If not for the one shot he took before having to leave his last game, six minutes into it, due to injury, he would have averaged 2.4 more field goal attempts per game than he has in games played with McGrady. This makes sense since with McGrady absent more of the offensive load would fall on Ming's shoulders. Unfortunately, these added shots have not translated into extra points since Ming is only averaging 24.0 points per game in those contests. What it has translated into is a much lower true shooting percentage, 57.3% to be exact. Ming has simply not been able to raise his game to a higher level without McGrady.
McGrady has made up for Ming not being on the court, though. Like Ming, McGrady has taken more field goal attempts per game when playing alone, averaging 5.2 more shots per. Unlike Ming, these added shots have been Rumpelstiltskin-ed into more points. When McGrady is forced to pass the ball to Ming, he has averaged 21.0 points per game. Without that burden to pass hanging over his head, McGrady has posted 28.8 points per game. He has done so by maintaining his shooting percentage, even shooting a little better when he shoots more (51.8% TS to 48.9% TS). In fact, it would most likely do wonders for McGrady and return him to the scoring numbers that first made him famous if he never had to play with Ming again.
These two players are only one example of what is happening across the NBA. With this sort of evidence, in addition to how the team as a whole does when one star is missing as compared to another, teams can make more informed decisions about which star is the more expendable.