Fesenko played limited minutes against subs; Millsap plays big minutes against starters. When Millsap and Al are on the court at the same time, their numbers are equivalent (On-Court). Consequently, Millsap's On-Court/Off-Court superiority (v. Jefferson) can only be explained through Al/Sap playing with other frontcourt players. That is, the Jazz have been better defensively with Millsap/Favors+Millsap/Kanter (and other frontcourt combos featuring Millsap but not Al) than with Al/Favors+Al/Kanter. Given the low number of minutes Kanter played last season, and his virtually even On-Court/Off-Court team defense numbers, it's a near certainty that Favors/Millsap was a hell of a lot better defensively than Favors/Al last season (obviously, without controlling for the other 3 dudes on the court).
Basketball is a team game. Unfortunately, the average fan seems completely unable to grasp team dynamics, and the piss-poor boxscore doesn't help. It's not a coincidence Millsap was 2nd in the NBA in adjusted +/- last season, and 5th over the last 2 (caveat: I don't know the methodology used to compute these stats, and suspect confidence intervals are HUGE).
Of course, as you've shown repeatedly in the past, you're not particularly analytical.
What are you trying to argue? Do you really think the Jazz were worse defensively with Fesenko than with Boozer/Memo?