Tavares Gooden's reaction when he looked at the stat sheet and saw Chicago's Devin Hester had minus-1 yard on three punt returns Monday night?

"Thank you, Lord," the 49ers linebacker said. "That's what I say, man. I just thank the Lord that we covered our butts off."

In addition to divine intervention, Gooden also credited chemistry for San Francisco's much-improved work in covering kicks over the past four games.

Beginning with a 13-6 win over the Seahawks, the 49ers have allowed an average of 2.8 yards on 12 punt returns (they allowed 17.1 yards per return in their first six games) and have surrendered an average of 21 yards on 10 kickoff returns (33.1 in first six games).

Most impressively, the four-game stretch includes contests against two of the NFL's top punt returners: Hester and Arizona's Patrick Peterson, who had 15 yards on four returns in a 24-3 loss to San Francisco on Oct. 29.

What's changed?

"Team chemistry," said Gooden, who has a team-best seven special-team tackles. "Guys have played a few games together. This special teams unit was basically separated due to some things going on in the offseason ... we just had to learn to play off each other."

The 49ers lost two special-teams stars, Blake Costanzo and Colin Jones, in the spring and struggled so much early that Gooden sought out extra meetings with special teams coach Brad Seely to improve his play.

"I think we saw it in ourselves that it's not just going to be one guy to replace (Costanzo). Everybody has to step up," Gooden said. "And that's what we did over these past three or four weeks."

Mimicking Sproles: Second-round pick LaMichael James played the role of Saints elusive running back Darren Sproles convincingly in practice, Gooden said.

James, who hasn't played this season, wore Sproles' No. 43 and ran patterns against San Francisco's linebackers. In the divisional playoffs last season, Sproles had an NFL-postseason record 15 catches for 118 yards and a 44-yard touchdown against the 49ers. Sproles is expected to play Sunday after missing the past three games with a broken hand.

"(James has) been helpful this week, I'll tell you that," Gooden said. "If Sproles is playing, we'll be ready for him. ... They look the same to me."

Briefly: Bellowed left guard Mike Iupati after the media entered the locker room: "Scott Tolzien is the starting quarterback." ... In addition to Alex Smith (concussion), who is questionable, the 49ers listed 10 players as probable on the injury report.