Amar'e's numbers started taking a hit in January. This was after he played about 40 minutes per game in December and averaged 30ppg and 10rpg shooting 55%.
In January, he played about 35minutes per game, averaging 25ppg on 45% shooting which I believe is the first time in YEARS he had a full month under 50% shooting.
It's possible that the ridiculously heavy minute load Amar'e carried in December, when he was unquestionably the MVP of the NBA, wore him down. He seems less active on defense to the eye. And it is backed up by stats - he's only averaging .8 blocks per game in March after being over 2 blocks for most of the season. He's averaging around 7 rebounds since January after averaging 9 before that, including averaging 10rb in December.
I think one factor that people are overlooking in wondering what is going on with this team is that this is NOT the same Amar'e - he's scoring a lot on mid-range jumpers, not exploding for a ton of dunks, not blocking anywhere near the ammount of shots he used to, not getting the amount of rebounds he used to.
And, as someone else pointed out - we went on a 8-14 from December 28th to that game against New Jersey that Amar'e had to sit out with an injury.
It's possible the heavy load he had to carry wore him down and he's just not the same player right now.