The Knicks were able to make this move thanks to a trade prior to the deadline that sent Ronnie Brewer to the Oklahoma City Thunder in exchange for a second-round pick (via Spears). They were at the NBA roster limit of 15 prior to trading Brewer, and shipping him off to Oklahoma City freed up a spot for Martin.
Before the signing became official, New York was not the only team in the mix for Martin. The Miami Heat appeared to be the front-runner for his services after shipping out Dexter Pittman and a second-round choice to the Memphis Grizzlies (per SportsCenter's Twitter feed).
It was later reported by Legion Sports' Twitter feed that the Heat were "atop" the list to sign Martin:
ESPN's Brian Windhorst also noted that the Heat were in contact with Martin, but that they planned on waiting until Mar. 1 to assess their options.
Unemployed for the entire 2012-13 season, Martin spoke at length about his struggles to find an NBA gig. He made it abundantly clear that his reputation as a malcontent personality preceded him, and told Spears in November that the characterization was "not accurate."
The Knicks will certainly find out over the next week-and-a-half.
Martin could instantly get playing time in Mike Woodson's rotation, as New York's front line has been depleted by injuries this season. Marcus Camby and Rasheed Wallace remain out of the lineup, and the Knicks could use some toughness on the inside.
Martin isn't the same player he once was, but toughness is something he never lacked. While with the Los Angeles Clippers last season, Martin averaged career-lows in points and rebounds but was an integral force to the Clippers' interior defense—especially in the postseason.
If all goes well, Martin will be able to do the same for New York this season. Still, getting through these first 10 days will be critical to the former All-Star's comeback.