Josh Levanthal wrote of Martinez:
Staying healthy continues to be Martinez's biggest obstacle. ...The two classic tools that matter most for Martinez are the hit tool and the hit for power tool. Now add a third tool, the ability to get his body in shape to withstand the rigors of a full professional season.
Martinez flashed his five-tool potential while in Buffalo, particularly the ability to hit with power to all fields. ...He can get overly aggressive at the plate, a weakness major league pitchers exploited during his time in New York.
A solid-average runner, Martinez shows good range and average arm strength in the outfield. He split time between left and right field in Buffalo, but he has held his own previously in center field.
Levanthal said of Niese:
iese's season of highs and lows came to a painful end in the big leagues. He tweaked a tendon in his right hamstring while stretching to cover first base in early August, then completely tore it off the bone on a warmup pitch, requiring season-ending surgery. His season got off to an inauspicious start as well, as he went 0-4, 7.96 in the first two months at Buffalo, but he recovered to dominate the IL for two months and pitch well for the Mets.
Niese's best pitch is a big-breaking curveball. He mixes it with a low-90s fastball that he can cut or sink, and a solid changeup that makes his fastball even more effective. Once he gained consistent command, he had little trouble with Triple-A or big league hitters.
Emphasis added. It wasn't just about command. As was discussed here during the season, Niese's improvements also had to do with refining his cutter, four-seam and two seam fastballs into unique weapons, and a better pitch assortment with more off-speed offerings.