RENTON — Gasping to catch his breath, his lip covered in blood, Walter Thurmond looked and sounded every bit like a person in the midst of an intense game of catch-up.

After missing more than three weeks of training camp with a high-ankle sprain, the second-year cornerback has finally been able to get back on the field this week, and Thurmond is doing every thing he can to get back to game speed with the season only a couple of weeks away. So if that means sprinting up the steep grass hill next to the practice field to get in some extra conditioning, Thurmond is all for that. And if it means playing with enough reckless abandon to end up bloodied in practice, well then that will be part of the plan, too.

“I’m just shaking this rust off,” he said while still catching his breath from the sprints up the hill. “… I had to wait the whole offseason, not doing anything and just train hard, and was really looking forward to camp, then the second day of practice I get hurt. So it just feels really good to get back out here. Got to stay healthy now.”

Staying healthy will be important not just for Thurmond, but for the Seahawks’ secondary as well. A team with many needs, the Seahawks could have taken a cornerback with their first-round pick, or tried to sign a big-name corner in free agency. But instead they used their top-two picks on the offensive line, and spent their biggest free-agency dollars on the offense. So if Seattle is going to improve a pass defense that has struggled in recent years — the Seahawks have ranked 27th, 30th, and 32nd in pass defense over the past three seasons — it will have to happen without any big-name additions.

And one reason the Seahawks think they’ll be better in the secondary is because they are expecting big things out of Thurmond, a fourth-round pick in 2010. Thurmond, who played sparingly last year after coming back from a devastating knee injury that ended his senior year at Oregon, was expected to compete immediately for a starting job this season. Only two days into training camp, however, he suffered a high-ankle sprain and missed more than three weeks of practice.

Thurmond finally was back in action this week, and despite being rusty, he is expected to play Saturday in Denver. And even in a few short days of practice, Thurmond has made plays that have the Seahawks excited about his potential for the upcoming season.

“He’s looked special,” Seahawks coach Pete Carroll said. “He’s looked very quick. … He looks very explosive. He’s much more together physically than he was last year at this time coming off the surgery and all that. It’s exciting.”

The surgery Carroll refers to was the one Thurmond needed to repair a torn ACL, MCL and PCL after hurting his knee in September of 2009. Prior to that injury, Thurmond projected as a second-round pick, possibly even a late first-rounder, so the Seahawks have felt since last year’s draft like they may have found a steal if Thurmond can get back to full speed.

“He was a fourth round pick that could have been a second-round pick or wherever, had he been healthy, and he shows that kind of explosiveness out here,” Carroll said.

Thurmond will get every opportunity to win the starting job at cornerback opposite Marcus Trufant, but for now he is mostly playing as the nickel back in passing situations. Carroll knows Thurmond won’t be fully up to speed with so little practice time under his belt, but he is still excited about watching Thurmond finally get on the field this weekend.

“We’re going to get him in,” Carroll said. “He’s going to play in the nickel position at least and get some work there, and we’ll look for some good things. But he has no practice backlog and he could easily make a couple errors out there and stuff, so we just want him to play some football and get on the field.”

Notable

In addition to Thurmond, two other players will make their preseason debuts this weekend, Carroll said. Defensive end Chris Clemons, who had offseason ankle surgery, will see limited playing time, and receiver Ben Obomanu, who had offseason shoulder surgery, will see significant playing time.

Running back Marshawn Lynch will not play because of a sore ankle. Carroll said the injury isn’t serious, and that Lynch would probably be able to play if it were a regular-season game. Also expected to be out are linebacker David Hawthorne (knee), safety Kam Chancellor (foot), and defensive ends Dexter Davis (hip) and Pierre Allen (hamstring). With Hawthorne and Chancellor out, rookie K.J. Wright and second-year player Josh Pinkard are expected to work with the starting defense.

The Seahawks currently have four players on the physically unable to perform list — WR Deon Butler (leg), DT Colin Cole (ankle), CB Roy Lewis (knee) and TE Cameron Morrah (toe). Carroll said Thursday that he isn’t expecting any of the four to be ready in time for next month’s season opener. If those players are on the PUP list to start the year, they’ll have to sit out at least the first six weeks of the season before being eligible to return.

Herald Writer John Boyle: jboyle@heraldnet.com. For more Seahawks coverage, check out the Seahawks blog at heraldnet.com/seahawksblog