JR Smith just tweeted that he’s going to sign with the Knicks, which is good news for Carmelo Anthony, because he’s finally got an ally on his side. (We’ll get to that later.)

Smith is a scoring machine who I knew well back in the day when he was tearing it up at St. Benedict’s high school in New Jersey. (His brother, Chris Smith, is a senior guard on Louisville.) Smith started out at Lakewood high school and then blew up one summer on the AAU circuit and became a national name. He was all set to go to attend UNC. But Smith’s rising talents – he wore 23 in high school and with his insane vertical leap, was doing crazy Michael Jordan-type dunks – drew the eyes of the NBA, and after he won MVP of the McDonald’s All-American game, it was a no-brainer.

He was the 18th pick in 2004, going to the Hornets after epic busts like Rafael Araújo (Toronto), Luke Jackson (Cleveland), Robert Swift (Seattle), Sebastian Telfair (Portland) and Kirk Snyder (Utah) were taken. Smith never really blew up as a pro until he got to Denver in 2006-2007, when he averaged 13 points a night and started to emerge as one of the league’s streakiest shooters and most valuable reserves. He’s got unlimited range, a slick handle (see below) and should be a deadly weapon for the Knicks on the offensive end.

When New York runs the pick-and-roll with Lin and Chandler, they can have JR Smith in one corner, plus Amare and Melo on the floor. The offense should certainly flourish. The defense? That remains to be seen. Guys most impacted by Smith’s arrival: Bill Walker and Steve Novak. Look for their minutes to diminish, perhaps rapidly.

As absurd as this might sound, Mike D’Antoni now has a problem on his hands – how long will it take him to figure out the team’s best lineup? Iman Shumpert is emerging as the team’s defensive “stopper,” but if he’s on the floor, then you sacrifice Smith’s 3-point shooting. Or do you keep Smith on the floor and move Amare to the bench because he doesn’t play D as well as Chandler?

Amazingly, this could be New York’s starting lineup and second unit: Chandler, Amare, Melo, Fields, Lin; Harrellson, Jefferies, Smith, Shumpert, Baron Davis. Walker and Novak will go from playing huge minutes the last two weeks to an end-of-the-bench role.

Smith’s arrival should briefly stop all the “Can Carmelo mesh with Lin?” chatter while everyone gushes over the signing. Well, until they lose a game. Then Melo will catch heat, but he’ll at least have his buddy JR Smith by his side. Melo will need him.