Still hamstrung by his ailing hamstring, Giants weakside linebacker Michael Boley sounded frustrated on Tuesday.

“It’s still not where I need it to be for me to be able to go out and work,” Boley said after running on it for the first time in “awhile.”

Boley said he feels a “pain” in his hamstring, and while the MRI he took at training camp didn’t reveal any bleeding, he said his body knows when something isn’t right.

This is the same hamstring Boley sprained last season, but the eight-year veteran insists the pain is in a different spot.

Obviously this isn’t a good time for Boley to be injured (when is?) because the Giants are trying to blend a linebacking core that doesn’t have extensive experience playing together. New acquisition Keith Rivers is joining second-year linebackers Mark Herzlich, Greg Jones, Spencer Paysinger and Jacquian Williams in addition to Chase Blackburn, whose played seven years with the Giants but was a free agent until Week 13 of last season.

“Very concerned about getting back out there,” said Boley, who served as a middle linebacker at times last season. “This is valuable time that I’m missing. You know, using this time to get in there and get my work with the first group and actually build that chemistry early, you know, it’s kind of frustrating to be honest.”

If there is a silver lining to the entire situation, it’s that Rivers, a natural weakside linebacker, has been able to see more reps with the first team.

“Rivers has played pretty well,” coach Tom Coughlin said. “He’s gotten better each week, practiced well, special teams he’s done a nice job. He can run.”

Of course, to hear Rivers describe his progress, you’d think he’d been struggling.

“I’ve got a long way to go,” Rivers said. “Still too many mistakes and I’ve got big dreams, so for me, I’ve got to keep my foot on the pedal. I’ve got to be hard on myself because I’m expecting a lot of myself and if I’m not, then I’ll ease up. And I can’t ease up.”

Rivers missed the 2011 season because of a wrist injury before being traded to New York from the Cincinnati Bengals, which is why he said he’s “having fun playing football again.”

The former USC standout hasn’t been forced to wear a protective cast on his surgically repaired wrist (he said he does a special tape job as a precaution) and, fortunately, the joint hasn’t been bothering him in the least.

“It’s holding up,” Rivers said. “I haven’t had any issues, surprisingly.”

Rivers’ health and understanding of the offense were really the only two questions about him coming into the season, so for him to say he’s feeling good is a major step in the right direction. And, if the former ninth-overall pick can master the defense, he feels he can contribute as a starter.

“You have to be in your book and you have to understand what you’re doing,” he said. “You can’t be playing and messing up the fits, messing up your drops. All summer long, I spent my time, I tried to do a few hours a night going over the stuff. But at the end of the day, when you get out there, you have to go mess it up live before you can really grasp it.”

Expect Rivers to be back with the first team this Friday as the Giants host the Chicago Bears at MetLife Stadium.

Follow the Giants and Alex Raskin @CBSSportsNFLNYG and @AlexRaskinNYC.