SANTA CLARA, Calif. -- You watch San Francisco wide receiver Anquan Boldin flash across the middle of the practice field, then turn to snag a Colin Kaepernick dart, and the first thing that comes to mind is: How in the world did Baltimore let this guy get away?

"I was actually thinking that to myself," said safety Donte Whitner. "How did they let him go? I don't know what their plan was or what happened over there. But he's a top-notch wide receiver in the National Football League. He showed it in the Super Bowl and he showed it all season long.

"Any time you lose a guy with that much production," said offensive coordinator Greg Roman, "it's definitely a blow. But that's the NFL. It's next man up. That's what this league is about.

"We felt bad that Mike got hurt, and he's getting better. But you can't blink. You move on. You've got to make it work."

The 49ers are. They have Boldin. They have tight end Vernon Davis, too, who seemed to gain Kaepernick's trust in the playoffs. Rookie tight end Vance McDonald has sure hands, while wideouts Kyle Williams and Quinton Patton, both of whom are hurt now, are possibilities. Mario Manningham might be, too, but he's on the team's Physically Unable to Perform list while recovering from a knee injury.

In the end, though, everything comes back to Boldin, mainly because every afternoon it seems he's the guy on the end of most of Kaepernick's deliveries -- just as Michael Crabtree was a year ago.

"I had that rapport with Kurt [Warner in Arizona]," Boldin said. "Then I had it with Joe [Flacco]. Now I see it growing with Colin.

"The great part about it is that there's been a lot of communication between us. Every play we're talking. It's like: 'What are you seeing? What do you like? What don't you like?' I think when you have that much communication it shows on the field."

It does here. And it should show up in the regular season. Just a hunch, but when you wonder where all those passes Kaepernick targeted for Crabtree go now, I would start with No. 81. 

" 'Kaep' is very comfortable with him now," Whitner said. "He's in the slot. He's on the outside. They're moving him around. 

"With every football that comes his way, 99 percent of the time he's going to catch it. So, yes, he can be the quarterback's favorite target. I'm glad Baltimore let him go."