The Giants signed running back Najee Harris on Tuesday and he said in a news conference that he believes he has “a good chance” to contribute because of the way John Harbaugh-coached teams approach offensive football. Before Harris can contribute anything on offense, he will need to prove that he is healthy. Harris tore his Achilles tendon while playing for the Chargers early last season and was cleared to return to football work a couple of months ago. Harris said Tuesday that he is not sure how long it will take him to return to full football shape, but that he is motivated by the opportunity to show that he has recovered well enough from the injury to have an impact on his new team. “I definitely start every year with a resentment, but this year even more so,” Harris said, via a team transcript. “I have a lot to prove as someone recovering from a torn Achilles tendon. Really everything I did in the past is in the past, and everything I do now is really what matters. I know there will be a lot of questions about how I get back and I’m ready to answer them all.” Harris never missed a game during four seasons with the Steelers and crossed 1,000 rushing yards in each of those years. He got most of those yards in small chunks (his career average is less than four yards per carry) and proving he can still be counted on in that role will be the first step in earning time in the Giants’ backfield.