If tight end is the "X'' factor in the Giants' revamped offense, then it's only fitting that Southern Cal rookie Xavier Grimble was signed as an undrafted free agent to compete for a job that is wide-open.

The Giants addressed wide receiver, running back and offensive line in the draft but passed on tight end even though it's a key position in the West Coast-style passing attack being installed by new offensive coordinator Ben McAdoo.

Moments after the draft ended, the Giants were on the phone with Grimble, who caught 69 passes for 731 yards and 11 touchdowns in three seasons before leaving USC a year early to enter the draft.

Grimble expected to be selected anywhere from the third to sixth rounds, but he lasted all seven rounds. As soon as the draft ended, he fielded calls from the 49ers, Falcons, Redskins and Raiders in addition to the Giants.

"They were the first team to call,'' Grimble said of the Giants. "I felt like they showed the most interest. They were genuine. The Giants are a great organization. It was kind of a no-brainer, really.''

Grimble joins a roster that has five tight ends, including 2012 fourth-round pick Adrien Robinson, who has played in only three games and hasn't caught a pass in two seasons. He is joined by free agents Larry Donnell (three catches last season), Daniel Fells and Kellen Davis.

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Former USC coach Ed Orgeron said Grimble has All-Pro potential. "I think I bring versatility,'' Grimble said. "I want to be the guy who can block and catch passes. I want to have an all-around game.''

After being assigned No. 89, the same number former Giants great Mark Bavaro wore, Grimble took it upon himself to learn about Bavaro and admired what he saw on video. "I had heard his name a few times,'' Grimble said. "I ended up going to my computer to find some highlights and read a couple of biographies to see how he did it. It was pretty cool to see he was a great player.

"I always like to look at guys who were great before and look at what they did and mold yourself after that. That's kind of my thing, to look back and try to envision myself doing the same type of thing.''

Fancying himself as a connoisseur of the tight end arts, Grimble also has studied Saints tight end Jimmy Graham, former standouts Jeremy Shockey and Kellen Winslow, and as far back as John Mackey.

After playing through a shoulder injury last season at USC and facing a third coaching change, Grimble decided it would be better to turn pro now. As surprised as he was to go undrafted, he was relieved to receive so much attention as a free agent.

"There's a ton of undrafted free agents and late-round picks that are great players,'' Grimble said. "I think it's all about the opportunity you get and what you do with it.''

The Giants could pursue free agent Jermichael Finley, who played under McAdoo with the Packers. But for the time being, third-year veteran Robinson has been given a golden opportunity to stake his claim to the starting job. He did little as a rookie and missed most of last season with foot and knee injuries.

Robinson's weight soared to 285 last year, but he's down to 270 with plans of playing at 265 and hopes of living up to the hype about his athleticism. General manager Jerry Reese called Robinson the "JPP of tight ends,'' comparing him to defensive end Jason Pierre-Paul, whose raw talent made up for his limited experience.

"Obviously, there's a huge opportunity,'' Robinson said. "They didn't draft anybody or bring in any big names. It's my third year, we've got a new OC, new tight ends coach, everything is fresh. It's like a clean slate. I'm just ready to go.''

Robinson likes what he's seen of McAdoo's offense and the way it moves the tight end around to use him in a variety of ways, including out of the backfield.

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"They laid the opportunity right in front of me,'' Robinson said. "I just have to take it and make the most of it. It's going to be now or never. That's my mentality that I'm taking every day.''