When linebacker Michael Boley was injured and missed time late last season, it created havoc for the Giants' defense. They lost four straight games, went through a string of possible replacements, and did not settle back into their Super Bowl-winning form until he returned in mid-December.

Boley again has been sidelined by a hamstring injury this summer, causing him to miss most of the preseason. It's a cause for concern, but there are two main reasons why the Giants are not panicking. First, it's still the preseason. And second, this year they have Keith Rivers.

Rivers, who was acquired in a trade with the Bengals during the offseason, has been able to step into Boley's place with the starting defense and perform at an impressive level. He may not have the knowledge and understanding of the entire defense that Boley possesses, but he did lead the Giants in tackles against the Jets on Saturday and has been making impressive plays in practice.

"He's definitely a seasoned veteran," Mathias Kiwanuka said of Rivers. "He's professional about his craft. He fits into the type of guys that the Giants really go after. But he's definitely an athletic linebacker who can cover some distance."

Rivers said he's feeling comfortable with his new team after four seasons with the Bengals. But he did mimic pulling out a language-to-language dictionary to illustrate that his comfort does have a limit.

"Here and there, I'm traveling and I have to look at my little book," he said. "What's this word? It's getting there."

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When he arrived, Rivers was focused on just making the team. Now, with Boley sidelined and the regular-season opener less than two weeks away, he could wind up being a starting linebacker for the Giants.

"I view myself as a person who could start, yes, definitely," Rivers said. "I've been that. I've shown to be capable of doing it . . . [I'll] just take advantage of the opportunities and hopefully that comes into fruition."

Rivers looked his best against the Jets, when he was flying in from the backside to make tackles in the running game. That's when he was able to show his speed and athleticism that made him the ninth overall pick in the 2008 draft.

He did not play last season because of a wrist injury, so the game against the Jets was the first time in a long time that he was able to play with some abandon.

"It's fun to be back having fun playing football," Rivers said. "It's a rough game and it's good to be having fun doing it and enjoying it. Just feeling like this is what you're supposed to be doing."

Rivers may be fitting in, but the Giants still will miss Boley if he is unable to play in the regular season.

"He's one of those guys who helps everybody else be a better player when he's out there on the field," Kiwanuka said of Boley. "He's one of those players who can play above the Xs and Os because he's been through the fire, he's been tested, he understands it, he gets it. As a group, we're going to have to step up and account for that."

Rivers will help, though.

"I've got big dreams, so for me, I've got to keep my foot on the pedal," Rivers said. "I've got to be hard on myself because I'm expecting a lot of myself. I can't ease up."

Certainly not now, when the Giants might be needing him the most.