SANTA CLARA To prepare for Aaron Rodgers' powerful right arm, the 49ers' defenders have been playing catch with someone with an even stronger one.
"I've never caught a football as hard as (Colin) Kaepernick throws," said safety Donte Whitner. "I don't know if they measure how hard quarterbacks throw in the NFL, but I guarantee Kaepernick's in the top five."
Whitner noted that Rodgers threw only six interceptions last season, but he said defensive backs dropped several of his passes because they couldn't handle the velocity.
That's why the defensive backs have tapped Kaepernick this week. The second-year passer had the strongest arm of all the quarterbacks in the 2011 draft.
"You catch one of his passes, and your hands will be burning," Whitner said.
Kaepernick also could see some snaps Sunday against Green Bay.
Offensive coordinator Greg Roman hinted that the read-option plays that were so successful for Kaepernick in the exhibition season he had a 78-yard touchdown run on one of them could be utilized in the regular season.
After all, Roman and Jim Harbaugh used that play at Stanford with Andrew Luck and his top backup, Alex Loukas.
"I think Kap gives you the flexibility to be able to talk about that and feel good about it and plan for it," Roman said. "I think it's just a good change of pace and makes the defense prepare for something different. So it's definitely a possibility."
Williams in the spotlight Ted Ginn missed his second consecutive practice because of a sprained ankle, increasing the likelihood that Kyle Williams will be the 49ers' punt returner in Green Bay.
Also absent was running back Brandon Jacobs (knee), whose once-pronounced limp is hardly noticeable but who also seems unlikely to play Sunday.
If that's the case, rookie LaMichael James will be active for the game and back up Williams on punt returns.
Kendall Hunter likely will return kickoffs.
Anthony Dixon and Frank Gore will be tapped for short-yardage plays if Jacobs can't go.