The small forward claims that Stoudemire was part of the reason for his move to the New York Knicks in 2011, but the power forward has played in fewer than 80 regular season games since Anthony's arrival at the club.
The 29-year-old told ESPN: "As a friend, it's hard for me to sit back and act like it doesn't bother me because I know how hard of a worker he is [and] I know the time that he puts in the gym to train and rehab. To see him go forward and then take some steps back every time, it's just sad.
"He was one of the reasons why I wanted to come to New York. So for me not to have that chance, the opportunity to get a full season in and get a rhythm going with him, it's not something I thought would happen.
"It's another weapon that we need. We could have used him last season at certain points. For him to get a fresh start off of this season, we need him. He's a big key to this team's success."
Stoudemire averaged 14.2 points per game in 29 fixtures.