NC Times By: JAY PARIS - Staff Writer SAN DIEGO ---- Darren Sproles is contemplating how deep is deep at Invesco Field at Mile High. "If it's real deep, I'm not going to bring it out," said Sproles, who was stellar in returning kicks in the opener. "But if it's like 2 yards? Yeah, I'll bring it out." The kick-return and kick-coverage teams were the least of the Chargers' worries in their recent loss to Dallas. Sproles, in his first NFL game, had returns of 49, 46 and 31 yards, and nearly broke two attempts for touchdowns. But Sproles, the team's fourth-round pick, realizes the thin air of Denver could cut into his returns. Broncos rookie Paul Ernster will try to give Sproles second thoughts of weaving through Denver's spotty coverage by burying his kicks in the end zone. If so, Sproles will hear the chirping of special teams coach Steve Crosby in his ears: "Kneel down, kneel down." If not, the 5-foot-6 Sproles' posse will encourage him to do his thing. "I think he will become one of the best in the business," said linebacker Shaun Phillips, who delivered some important return blocks versus the Cowboys. "To be that size, that fast and that quick, it's crazy." Some thought the Chargers were loony for taking a chance on Sproles, the shifty back who rewrote Kansas State's record book. "I think everybody knows about him from college, but a lot of people underestimated him because of his size," said linebacker Stephen Cooper, another one of Sproles' blockers. "But he has a real big heart." He also has a lofty NFL standing. After one week, he's the league's second-leading returner, averaging 36.5 yards per effort. "He's a great returner because he knows how to handle the ball and is real hard to tackle," Cooper said. "He's really quick." That hasn't gone unnoticed by the coaching staff. Coach Marty Schottenheimer said Sproles could see time at running back on offense. That's fine with Sproles. "They say I am," he said. "We'll see." After one week, seeing is believing in regard to Sproles' talents. Fonoti a go Left guard Toniu Fonoti returned to practice and will start Sunday in Denver. Fonoti will wear a protective cast on his broken right hand. Fonoti suffered a hairline fracture Wednesday and skipped practice Thursday. But Schottenheimer never thought it would prevent Fonoti from facing the Broncos. "I didn't see any evidence of uncertainty or hesitation on his part," Schottenheimer said of Fonoti's practice Friday. The news isn't as optimistic for defensive end Igor Olshansky (ankle, knee) and wide receiver Vincent Jackson (calf). Neither practiced. Although they aren't officially ruled out, it's obvious they won't play Sunday. Jacques Cesaire will replace Olshansky at right end, and first-round pick Luis Castillo will make his NFL starting debut at Cesaire's left end spot. Linebacker Shawne Merriman (knee) continued to work without setbacks and is fit for this weekend. No fine for Castillo Castillo not only gets his first start Sunday, but he learned Friday the NFL will not fine him for striking Cowboys quarterback Drew Bledsoe's helmet last Sunday. "That's awesome," said Castillo, who drew a 15-yard roughing the passer penalty. "It was completely incidental." Castillo is equally thrilled about trotting out with the first unit in his initial visit to Invesco Field at Mile High. "That was my goal coming in, and unfortunately I got hurt (strained Achilles' tendon in camp) and I got a great guy (Cesaire) playing in front of me," he said. The transition from Northwestern to the NFL ---- as well as from tackle to end ---- hasn't slowed Castillo. "Playing a 3-4 end is a lot like playing a tackle in the 4-3 defense," he said. "It's a lot of the same stuff." Quick hits CB Jamar Fletcher said published reports of him being upset about not playing on Sunday were "taken out of context." Sammy Davis, who got burned for the game-winning touchdown, and not Fletcher, was the team's nickel back. "I'm good; I'm never frustrated," Fletcher said. "I'm just out here to try and help this team whenever I'm called on." ... The Chargers recently worked out these free agents: LBs Roger Cooper and D.D. Acholonu; WRs Jimmy Farris, Drew Haddad, Triandos Luke, Chauncey Stovall and Ben Steele; DBs Terreal Bierria and Aric Williams, TE Brock Edwards; and DE Jonathan Jackson. ... WR Reche Caldwell left practice early because of a sore right knee.