SANTA CLARA -- When it comes to exhibition openers, 49ers quarterback Alex Smith learned a valuable lesson last year in New Orleans.
"Wear your mouthpiece," said Smith, who sorely missed his during that 24-3 loss to the blitz-happy, bounty-hunting Saints.
Michael Crabtree could use any such tips for Friday night's exhibition opener against the Minnesota Vikings at Candlestick Park. Crabtree is slated to start in what will be the first exhibition game of his four-year NFL career, coach Jim Harbaugh said Thursday.
Ted Ginn Jr. will be the 49ers' other starting wide receiver, and that won't preclude Randy Moss from making his 49ers debut, Harbaugh said.
Crabtree missed seven practices because of a calf strain before returning to team drills Tuesday. Ginn, Harbaugh said, has had a "great" training camp, showing no signs of a leg injury that sidelined him in offseason workouts and the NFC Championship game.
For Moss, it will be his first appearance in an NFL uniform since 2010, when his three-team tour included a Vikings stint in between those with the New England Patriots and Tennessee Titans. Moss launched his prolific NFL career with the Vikings from 1998-2004 before getting dealt to the Raiders.
Other wide receivers who'll likely make their 49ers debut: Mario Manningham, the New York Giants' Super Bowl hero last season, and A.J. Jenkins, this year's first-round draft pick.
Harbaugh declined to state how long his starters will play.
Smith likely won't need his mouthpiece too long before giving way to Colin Kaepernick. But Smith is looking forward to any action, noting: "This is real ball. It's been a while since we've had that. It'll be fun."
Here are four areas to keep an eye on during the exhibition season's opening four quarters:
1. Kyle Williams, Ginn's infamous replacement at punt returner in that 20-17 overtime loss to the Super Bowl-bound Giants, will "most definitely" get another chance to return punts. Don't look at this as a therapy session, however. "It's part of the depth chart. He returns punts for us," Harbaugh said.
How should 49ers fans react to Williams' presence? Harbaugh answered: "He's a 49er. He's one of us."
Although Williams drew Harbaugh's wrath for fighting Wednesday with rookie cornerback Deante' Purvis, Harbaugh said he and Williams "will be better for it."
2. For the first time since last exhibition season, Kaepernick will fire passes before halftime of a game. Kaepernick, limited to three regular-season cameos his rookie year in 2011, should finally see significant action upon relieving Smith.
It will be Kaepernick's first test to separate himself from Josh Johnson and Scott Tolzien in the race for the No. 2 job. Johnson, an Oakland native and former Tampa Bay Buccaneers backup, will be making his 49ers debut. Tolzien's last action came against the 49ers in last year's exhibition finale for the San Diego Chargers, who then waived him.
3. Two years ago, undrafted rookie Victor Cruz caught three touchdown passes in the Giants' exhibition opener; Cruz morphed into a 49ers' headache in January's NFC title game. Which undrafted free agent could surprise from these 49ers? Start with wide receivers Nathan Palmer, Brian Tyms and Stanford product Chris Owusu. Or marvel at how outside linebacker Kourtnei Brown's frame looks similar to starter Aldon Smith's.
4. Versatility goes a long way for bubble players vying for slim roster openings. Anthony Dixon will get a shot at fullback and running back. Several defensive players also might moonlight on offense: defensive linemen Demarcus Dobbs and Will Tukuafu at fullback; defensive backs Cory Nelms and Ben Hannula at wide receiver.