During last season’s heartbreaking loss at California, Arizona running back Nic Grigsby spent most of his time on the sidelines.

The senior tailback injured his shoulder during the fourth game of the season against Oregon State and wasn’t the same since, missing three full Pacific 10 Conference games and playing limited in six.

“”It was very challenging,”” Grigsby said of sitting out and limited playing. “”I started to lose my cool a couple of times because I wanted to be out there and be able to make plays for the team.””

Grigsby carried the ball zero times and caught one pass for six yards against Cal as he watched Arizona implode on its way to a 24-16 loss.

But as is the case for most Arizona players, 2010 is different.

He finally gets a shot to show the Bears and the Pac-10 what he can do at full health. Receiver William “”Bug”” Wright said he expects Grigsby to be “”a lot more vocal this year against Cal, especially since he didn’t play last year.””

But his 2009 absence isn’t the only motivating factor for Grigsby this weekend. Cal, a hotbed for top running backs, originally recruited the 5-foot-10 back out of Whittier, Calif.

“”I was his roommate freshman year and he was telling me they recruited him, but he chose Arizona over them so he’s going to try to do work against them,”” Wright said of Grigsby.

Cal, and the Pac-10 for that matter, will no longer be dealing with a hobbled Grigsby. In fact, the 2010 version of Grigsby is even more electric than the back that would rip off 60-plus yard runs at any moment last season.

“”He seems a little bit more explosive. I think he had a great offseason,”” said running backs coach and co-offensive coordinator Seth Littrell. “”I think he worked real hard in the spring and the summer months. It seems like he has a little extra gear than he had this year.””

Quarterback Nick Foles said that Grigsby “”had the best offseason he’s ever had here,”” and it’s showed in 2010 despite playing in a pass-happy offense — five touchdowns and a 5.7 yards per carry average.

But the Golden Bears have a star running back of their own who the Wildcats have to keep an eye on, Shane Vereen. The 5-foot-10, 204-pound junior is leading the Pac-10 in rushing yards with 324 — 117 more than the next back.

Vereen is coming off of a 198-yard, three-touchdown game from last week in a loss to Nevada, and torched Arizona last season for 159 yards and a 61-yard touchdown in the absence of current Detroit Lion Jahvid Best.

“”He’s about as good of a back as there is in the Pac-10 and probably the country,”” Littrell said of Vereen. “”I think he’s very explosive and can make a lot of plays. You have to key on him every single snap and understand that he can take the ball 100 yards anytime he touches it.””

Co-defensive coordinator Tim Kish described him as a perfect combination of power and speed, and senior defensive end Ricky Elmore recalled his resiliency from last year’s game when he turned a “”10-yard loss”” into a “”30- or 40-yard gain.””

But Vereen is much more than just another opponent to Grigsby. They both grew up together as running backs for California high schools.   

“”We know each other a little bit, so we’re going to go out there, chat before the game, wish him good luck and let the best team win,”” Grigsby said.

Both Grigsby and Vereen are coming into this game from completely different situations — Grigsby, as a player coming back from injury, slowly wanting to re-establish himself as potentially one of the best in the conference, and Vereen, who is already one of the Pac-10’s top backs.  

Although, as Littrell said Wednesday, “”We’re not going to win or lose a game by any one player.”” The battle between former Cal recruit Grigsby and his opponent and friend Vereen should be something special.

“”He’s a great back and I love watching other great backs too,”” Grigsby said. “”It’s going to be fun to go out there and compete with each other.””