Any trade for Millsap or Jefferson involving Pierce wouldnt make sense to me. Celtics would need Pierce's scoring still. The only reason it makes sense for Utah is if they decided it would be good to flip Pierce to someone else for something.
How would a Pierce for Jefferson trade not make sense?
In the games he started last season (regular and playoffs) Jeff Green averaged more than Pierce (> 20 PPG) and scored at a more efficient rate.
In the last 20-30 games of the season Jeff Green was clearly a more deadly offensive threat than Pierce.
Pierce struggles at SG and Jeff struggles at PF. Both guys need to play the SF spot in order for the Celtics to make the most of their talent - that means there's really only room for one of them, and only one of those guys is young and athletic enough to still be effective in the league 5 years from now.
On the other hand we only have a single center on our roster, and that is KG. The same KG who cannot play more than 25 MPG during the regular season, else we risk breaking him down. In addition to our Max 25MPG center we have a mediocre 6'7" PF who is barely starter material, and a young 6'9" PF who is just coming off a major back surgery.
Yes, we need bigs..and we needs bigs you are young enough and good enough to be able to stay on the court for 30+ minutes a night. We need rebounding, we need either inside scoring or interior defense. Jefferson gives us the rebounding and the inside scoring.
Last season Jefferson averaged 18 PPG - exactly the same number that Pierce averaged for us last season. Jefferson however shot at 50% from the field and grabbed 9 rebounds per night as well.
Jeff Green also shot over 50% from the field on his 20 PPG scoring last season as a starter.
Kevin Garnett has been an efficient scorer his entire career, he also shot 50% from the field last season.
KG is 7'0", Al Jefferson is 6'10" (and strong as an ox) and Jeff Green is an athletic and long 6'9".
That would make one of the most dynamic and deadly front courts in the league. Jefferson can dominate inside, KG can score inside or out (and make the most of his legendary jumper), and Jeff Green would apply constant pressure with his attacking off the dribble.
That front court combined with Rondo at PG would make us an instant contender, no matter who we start at SG.