I understand the sentiment, he hasn't been able to garner a great reputation thus far in his career.
Regarding Pietrus though, I think Terrence has a lot more potential as this point in their respective careers. Even this past season, despite floundering in Houston for first half of the season, he was able to show up in Sacramento and perform better than Pietrus statistically.
In 18 games his per 36 avgs:
15.5 pts, 7.2 rebounds, and 5.4 assists on 46.1% shooting
Pietrus was in 42 games:
11.3 pts, 5.1 rebounds, and 1.0 assists on 38.5% shooting
I do realize Pietrus was coming of injury, and is a better 3 point shooter.
Terrence is an excellent rebounder for his position, which is certainly something the Celtics could use.