To the team's detriment.
Big Al + Millsap provides more defense than it gives up in offense compared to Okur + Big Al. Okur should be relegated to the bench for the next two seasons, unless he proves to be a better player than Millsap or Big Al (he's not, and it's not really that close).
Starting Millsap and Jefferson, we have a very short starting lineup. Okur has been a very solid post defender, and opens up the court for Jefferson to a much greater degree than Millsap would. However, that lineup might not be mobile enough against some of the faster 4s in the league.
If the goalisthe Lakers, we are much morelikely to beat them starting Okur/Jefferson than Millsap/Jefferson.