Any defensive coordinator in the Pacific-10 Conference knows what the most difficult part of the Arizona football team’s offense is: junior tight end Rob Gronkowski.

Last season, Gronkowski posted huge numbers as a sophomore despite missing the first three games with mononucleosis. He tied for the team lead with 10 touchdown grabs to go along with his 627 yards on 47 catches — all single-season school records for a tight end.

“”He’s the kind of a guy where you’re going to have to use unbelievable technique, and you’re going to have to play a really good game to shut him down,”” said tight end coach Seth Littrell.

To try and get even more out of Gronkowski during his junior campaign, UA offensive coordinator Sonny Dykes visited the Dallas Cowboys during the offseason to learn more about how they use their stud tight end Jason Witten.

“”What I learned is just the importance of the quarterback understanding where the receivers are going to be,”” Dykes said. “”Whether it’s the tight end, the inside receiver or the outside guy.

“”Witten is (Dallas quarterback Tony) Romo’s best friend, so he’s going to throw a lot of balls to him,”” he added. “”That’s probably the biggest thing I’ve learned, is to get Robbie to take (Arizona’s quarterbacks) out to dinner.””

But Littrell has seen Gronkowski take a different route. Even with Gronkowski missing the bulk of fall camp with a lingering back injury — and being off limits to the media as a result — UA coaches have been noticing the effort level Gronkowski has been bringing to workouts despite being temporarily hobbled. Because as good as Gronkowski is now, Littrell said, he can still get better.

“”He comes out here each and every day and works hard, and he knows he has a lot of stuff to work on. He’s not where he needs to be right now,”” Littrell said. “”But his physical attributes, he’s got all that. Now he just needs to work on fine-tuning a lot of little things.””

And as soon as Gronkowski gets the green light to return to his full role on the team, and if he continues to get better, that could be a frightening prospect to opposing defenses around the Pac-10.

“”Robbie’s got to work on coming on and staying consistent every game,”” Littrell said. “”I think when he does that, when he comes out and he plays really well and he’s focused in, then he’s going to be hard to stop.””