TEMPE, Ariz. -- Arizona wide receiver Anquan Boldin briefly tested his sore hamstring on Thursday, then watched the rest of practice.
If Boldin can't play in the opener against San Francisco on Sunday, the Cardinals may look to Jerheme Urban for help.
"If for some reason they have to lean on me more in the game, I'm ready for that," Urban said after sweating out a practice on a 100-degree day.
Coach Ken Whisenhunt said he remains hopeful that Boldin will play when the defending NFC champions open the regular season in University of Phoenix Stadium, which was not sold out as of late Thursday afternoon.
"He came out early and did some limited work with us, and then we shut it down just so we wouldn't stress it," Whisenhunt said. "I really don't know where he is at this point. Hopefully, he'll continue to improve and we'll have a shot for the game on Sunday."
Meanwhile, wide receiver Steve Breaston, who is recovering from a bruised kneecap, participated fully in practice and is expected to play.
This isn't the first time Boldin has battled hamstring problems.
In the playoffs last January, Boldin injured a hamstring on a 71-yard touchdown catch in the first round against Atlanta and missed the second-round victory at Carolina.
"I don't know if I could compare those two [injuries], but I think Anquan's shown a history of trying to get back, and I'm hoping that that's what we'll have this week," Whisenhunt said.
For many teams, the potential absence of a Pro Bowl receiver could force drastic changes in the game plan. Not the Cardinals, who appear to have a stable of reliable targets for quarterback Kurt Warner.
Arizona's potent air attack has another Pro Bowler, Larry Fitzgerald, and Breaston is a capable No. 3 receiver.
If Boldin can't go, the Cardinals might also rely on Urban, a six-year veteran out of Trinity (Texas), who played all 16 games last year, catching 34 passes for 448 yards and four touchdowns.
The 6-foot-3, 212-pound Urban may have been the most improved player in training camp this year, and he said he's ready if the Cardinals need him on Sunday, or beyond.
"Obviously, we're a better team if we're all spread out with our big guns, so hopefully we'll do that," Urban said. "I'm not going to add any extra pressure to myself, because I've done the little things to get here to be ready for this opportunity if it presents itself."
Boldin's status is only one of the questions facing the Cardinals as they prepare for the season opener, which will feature an NFC championship banner-raising ceremony.
The offense, so reliable a year ago, also raised concerns as it sputtered through an 0-4 preseason. Urban said the players were frustrated with their poor showing in exhibitions.
"Obviously, we were running a lot of our base stuff, but we should have executed more," Urban said. "We can't really build on it if you can't do it, so to speak, but all of us have been playing together for two years now, and I think we've got a good enough confidence level with each other."
Throughout August, Whisenhunt cautioned against drawing too many conclusions because the team barely dipped into its playbook. Asked if he was happy with how his offense has looked in practice this week, Whisenhunt smiled and replied, "If it works on Sunday, then it'll make it look like I knew what I was talking about in the preseason. So hopefully that's what'll happen."