Only it's not Michael Crabtree, although the Panthers understand he'll bring an added dimension to the 49ers that wasn't there when the teams met in November.
It's actually not any certain receiver from the 49ers at all.
It's Steve Smith.
Not to devalue what Crabtree means to San Francisco. He had a monster game in Sunday's 23-20 victory over Green Bay, catching eight passes for 125 yards. I'm sure quarterback Colin Kaepernick is more effective when he has all of his weapons on the field.
But Smith means more to the Panthers.
Without Smith in the regular-season finale at Atlanta, Carolina wide receivers had four catches for 22 yards. Quarterback Cam Newton and the passing game struggled to get 149 yards, and 75 of that came on a screen pass to DeAngelo Williams that the running back fumbled away at the end.
So today is a big day for Carolina.
Today is when Smith, for the first time since spraining his left knee in the first quarter of a Week 16 victory against the New Orleans Saints, will practice with the team. Smith already has said he will play against the 49ers, but today will be the first day the Panthers will have an idea of how effective he can be.
The Panthers (12-4) need Smith if they hope to advance, more than the 49ers (13-4) need Crabtree.
You actually could argue that tight end Vernon Davis is more valuable to Kaepernick than Crabtree. With Davis on the field, Kaepernick has 21 touchdowns and five interceptions and a 101.6 passer rating. Without Davis he has no touchdowns, three interceptions and a 34.7 rating.
Davis left the first meeting against Carolina midway through the second quarter. With him the 49ers led 6-0, and it would be 9-0 two plays after he suffered a game-ending concussion.
Not that Kaepernick was lighting it up. The Carolina defense already had gotten to him for two of their six sacks and his rating was 74.0 when Davis left.
But back to why Smith is more valuable to the Panthers than Crabtree is to the 49ers. Smith was targeted a team-high 11 times against San Francisco in the 10-9 victory at Candlestick Park. He had a game-high six catches for 63 yards.
Four of those catches went for first downs, all in the second half. Two came in the fourth quarter, including a 9-yard reception with 2:18 remaining that allowed Carolina to run out most of the clock.
The other was a 6-yard pickup on third-and-19 from the San Francisco 41 that put Graham Gano in position for the game-winning 53-yard field goal with 10:05 remaining.
Carolina coach Ron Rivera called the catch with 2:18 left as "clutch as any I've been around."
"Steve likes to say in big games, big players make big plays," Rivera said the following week. "And that’s true. Steve is one of those guys."
Smith knows it, too. He cut me off when I tried to remind him of how clutch he was in the first San Francisco game.
"I have 13 years of clutch catches," he said matter-of-factly.
He's right. Smith's 836 career catches for 12,197 yards and 67 touchdowns may one day land him in the Hall of Fame. He's a big reason the 2003 team advanced to the Super Bowl.
Crabtree can only hope to get to that level one day with his 279 catches for 3,629 yards and 22 touchdowns.
Asked about the significance of both teams having their top wide receiver on the field this week, Smith answered in typical Smith fashion.
"I'm not on the same level as Crabtree," he said. "I'm just an old dude."
But as far as the Panthers are concerned, he's a valuable old dude.