NBA2k11 Rotation problems

I play for the Los Angeles Lakers and I signed Tracy McGrady. My starters would be Fisher, Kobe, Artest, Gasol and Bynum but McGrady will be the point guard in late moments of the game so I set his minutes higher than Fisher's.

The problem is Fisher is still the one who finishes games. I set McGrady's position as an SG/PG so that he can also play at point guard.

I want this lineup to finish games : T-Mac, Kobe, Artest, Odom and Gasol. No problem with Odom though as the sixth man, I only got problem with McGrady.

Same with Shaq in the Cavs, I want Andy to finish games but still Shaq is the one who gets the position at center. Please help, is this a glitch?

Not a glitch. The starters usually finish the game in 2K if you're on auto-sub.
You can do it the other way around. Start T-Mac and Varejao but give them less minutes than Fisher or Shaq.
Or you can do manual subs.