Whereas quarterback Troy Smith has just four starts under his belt for San Francisco and running back Brian Westbrook just stepped in for the injured Frank Gore last week, wide receiver Michael Crabtree and tight end Vernon Davis were very much a part of the 49ers’ near-comeback at Lambeau Field a year ago.

So here’s a look at each of those four key skill players for San Francisco, known and unknown:

The Unknown: Smith and Westbrook
The oft-used word this week to describe Smith, the former Heisman Trophy winner from Ohio State, is that he’s given San Francisco a “spark” in leading them to three wins in their last four games after a 1-6 start. But like any inexperienced quarterback – Smith had just two NFL starts in his career, both as a rookie with Baltimore in 2007, before a month ago – it’s hard to get a complete handle on him.

He posted a quarterback rating of 115-plus in each of his first two starts this year with combined stats of 29 completions in 47 attempts for 552 yards with two TDs and no interceptions. But his rating has been less than 62 in each of his last two starts (combined 27-of-54, 277 yards, one TD, two INT).

He’s also talked about as a mobile quarterback, yet he’s only compiled significant rushing yards in one game (5 carries for 45 yards vs. Tampa Bay in Week 11) and he was sacked a total of 11 times over a two-game span against the Rams and Buccaneers (Weeks 10-11).

But the Packers aren’t as focused on the stats as what they’ve seen on film, and that’s an athletic quarterback who can keep plays alive with his feet, and a strong-armed thrower who can get the ball deep down the field if need be.

“Anytime you face a mobile quarterback, especially one who can throw outside the pocket, it makes it a lot tougher on you,” Packers defensive end Cullen Jenkins said. “With a team like San Francisco, you have to concentrate on the run game first, so you have to worry about getting that contained.

"Then when you move onto the pass, it’s not just about getting after the quarterback, it’s about getting after the quarterback but make sure you keep him contained. Don’t let him get outside the pocket, lose contain and let him scramble and throw.”

That first priority, stopping the run, now centers on Westbrook after Gore left last Monday night’s game against Arizona with a hip injury after five carries in the first quarter. Westbrook, a nine-year veteran, had only five carries on the season prior to Monday but posted 23 rushes for 136 yards and a touchdown in Gore’s place, looking like a “fresh-legged runner,” according to defensive coordinator Dom Capers.

“When the next step down from Gore is Westbrook, that’s pretty impressive,” Jenkins said. “You can’t go in there saying, ‘Oh, they don’t have their leading rusher, we’re going to get after them.’ You can’t think like that, because you know what Westbrook can do, and Westbrook has been a prime-time player in this league for a while.”

Packers fans will no doubt remember some big games Westbrook has enjoyed at Green Bay’s expense in the past playing for Philadelphia. In 2004, he caught 11 passes for 156 yards and three TDs out of the backfield in a 47-17 Eagles romp, and in 2005, he rushed 20 times for 120 yards and a TD in a 19-14 decision.

Westbrook’s return to the spotlight on Monday, combined with the work of rookie Anthony Dixon and Gore (before he got hurt), helped the 49ers bull their way to 261 rushing yards against the Cardinals, the most by a San Francisco team since 2006. That certainly raises eyebrows, especially after the Packers gave up 110 yards on the ground to Atlanta’s Michael Turner last week.

But nose tackle B.J. Raji insists the two running games are dissimilar in style, so it’s a whole different set of challenges up front this week.

“Atlanta attacked us on the edge, to make our corners tackle big Turner,” Raji said. “This team is different. They’re trying to hit plays downhill, in the A and B gaps.”

That straightforward approach is based on the offensive line the 49ers have constructed. When at full strength, their line consists of three first-round draft picks in left tackle Joe Staley (2007), left guard Mike Iupati (2010) and right tackle Anthony Davis (2010), and two second-rounders in center David Baas (2005) and right guard Chilo Rachal (2008).

Currently, veteran Barry Sims is filling in for an injured Staley, but nonetheless, the 49ers’ talent creates a formidable unit.

“That’s what I’m here for,” Raji said. “I’d like to think when (GM) Ted (Thompson) was thinking of drafting me, he wasn’t thinking of drafting me for a game like last week. He was drafting me for this kind of game – a big ol’ offensive line, they’re going to try to come out at you and move you off the ball, and it’s my job and our job to anchor ourselves down and make plays.”

The Known: Crabtree and Davis
These two were as responsible as anyone for the 49ers’ rally from a 23-3 halftime deficit last season at Lambeau Field in what became a tight, 30-24 Green Bay win.

Crabtree, in his second year as a first-round pick out of Texas Tech, made two big plays in that second half, hauling in a 38-yard touchdown in the third quarter and then posting a 35-yard reception in the fourth that helped set up the score that pulled San Francisco within six points with just under 6 minutes left.

Meanwhile, Davis, a first-round draft pick in 2006, had five catches for 104 yards in that second half after just one catch for 4 yards in the first. The 6-foot-3, 250-pounder made back-to-back grabs for 11 and 29 yards preceding Crabtree’s 38-yard TD, and then he added a 24-yard TD of his own.

This season Davis’ numbers (40 catches for 548 yards and four TDs) are well off the pace of his breakout season a year ago (48 catches, 965 yards, 13 TDs), but his combination of size and speed at the tight end position still makes him a difficult matchup for any defense.

“He can really run,” Head Coach Mike McCarthy said. “He’s a powerful man, and he has the ability, when you can stretch a defense vertically like he does, it not only gives himself opportunities, but it makes the guys on the outside better.

“I’m a big believer in the fastest way to the end zone is through the post. You can never have enough big guys that can play inside and stretch it, and I think he’s definitely one of the premier big guys in the league to play inside and get vertical.”

Crabtree and Davis each have just one 100-yard game apiece this season, but they came in the same contest when the 49ers nearly upset the Eagles in Week 5, losing 27-24. That was before Smith was throwing the ball to them, but those pass-catching combos have had better than a month of game experience together now.

How the Packers cover Davis will be the most intriguing question now that the defense's top cover linebacker, Brandon Chillar, is out for the season. Capers may go with cornerback Charles Woodson on Davis, or he may use a combination of players to keep things changed up.

“This is a talented team,” Capers said. “You look at the talent at their skill positions. We saw it last year. We played probably as good a first half last year as we played all season (holding the 49ers to 57 yards and three points). They ran very few plays after that first series, and had four three-and-outs in a row.

“But that second half they got it going, and once they got it going, we had our hands full.”

Additional coverage – Dec. 3