SANTA CLARA, Calif. -- In the hours before making his NFL debut, San Francisco 49ers quarterback Nick Mullens said he got a good night of rest.

"I slept good except I woke up about every hour," Mullens said, laughing. "But those hours were great. I slept pretty good."

If that qualifies as a good night of sleep, Mullens had to feel as if he were living out a dream Thursday night against the Oakland Raiders.

Mullens, a 2017 undrafted free agent out of Southern Miss, began the day by receiving a good luck text from fellow Golden Eagle Brett Favre. He ended by receiving a congratulatory call from Favre and approximately 600 congratulatory text messages from other friends and family.

In between, Mullens put together one of the greatest statistical performances by a quarterback making his debut in NFL history and led the 49ers to a convincing 34-3 victory against the Raiders.

Mullens, who replaced an injured C.J. Beathard as starter, was unfazed by his prime-time debut, calmly directing the Niners to touchdowns on the first two drives of his young career and going on to post the best passer rating by a quarterback in his first start since the merger in 1970.

"You never know until you see someone," 49ers coach Kyle Shanahan said. "He didn't surprise us in terms of, the game's not too big for Nick. He's very poised. He is always locked in. The guys, they respect him. He earned a lot of respect in the preseason, them watching him play. Both years, last year and this year. The way he handles himself in practice each week. He didn't really know for sure whether he was going to start today, until today, and just the way he handled the two days of long walk-throughs and stuff.

"He's a machine in there and I was happy for him."

With Mullens at the helm, the 49ers blew out the Raiders in what was the final "Battle of the Bay" before the Raiders relocate to Las Vegas.

By the time Mullens' first regular-season playing experience was done, he was 16-of-22 for 262 yards with three touchdowns and no interceptions for a passer rating of 151.9.

With each completed pass, Mullens seemed to reach another historic benchmark.

• Mullens' passer rating of 151.9 was the best by a quarterback making his debut with at least 20 attempts since 1970.

• That passer rating was the highest by a 49er since Alex Smith had a rating of 157.1 on Oct. 29, 2012.

• Mullens joined Marc Bulger, Ryan Fitzpatrick and Marcus Mariota as the only players over the past 25 seasons to throw for three or more touchdowns in their first game, according to ESPN Stats & Information research.

• Mullens is the first player since Carson Wentz to throw for a touchdown in his first career game on the team's opening drive, and one of four to do it in the past 15 seasons, along with Wentz, Mariota and Matt Ryan.

• Mullens joined Fran Tarkenton (1961) and Jim Kelly (1986) as the only quarterbacks to throw for 250-plus yards, three-plus touchdowns and no interceptions in an NFL debut since 1950.

• Mullens is the first player in 49ers history to throw for three touchdowns in his first game with the team, according to Elias Sport Bureau.

• The last time a 49ers quarterback threw two touchdown passes on the first two drives of a game was Colin Kaepernick in Week 4 of 2016. The last time the Niners scored a touchdown on their first two drives of a game was Week 14 of 2016.

Things went so well for Mullens on Thursday night that his previously unverified Twitter account was granted a blue check mark -- during the game.

All of that added up to the Niners' second win of the season in one of the biggest blowouts by a team with only one victory this late in the season in the Super Bowl era. The Niners' 31-point margin of victory is the second largest in that category.

The 49ers signed Mullens in 2017 as an undrafted free agent out of Southern Miss, where he was the most prolific quarterback in school history, surpassing Favre along the way and ultimately shattering Titans quarterback Austin Davis' records.

Before Thursday's game, Favre tweeted good luck to Mullens, which might have helped his case for verification, and sent a text message to Mullens that said, "No pressure, just be yourself."

Best of luck to my fellow @USMGoldenEagles alum and QB @NickMullens tonight for the @49ers! #SMTTT — Brett Favre (@BrettFavre) November 1, 2018

Immediately after the game, Favre called Mullens.

"It was pretty cool, definitely an honor," Mullens said. "It's cool to see Southern Miss alumni stay in tune with the program and support each other. Definitely appreciative of that and definitely have the most respect for Brett. He just told me how proud of me he was."

In the days leading up to Thursday's game, Mullens prepared as though he would start, but the Niners held nothing but walk-throughs because of the short turnaround from Sunday's loss to Arizona.

With Beathard attempting to recover from his injury, the Niners weren't even sure who would start until things started trending in Mullens' direction Wednesday night. Shanahan informed Mullens of that decision but still put Beathard's injured right wrist and thumb through a pregame test Thursday to determine if he'd be available to back up Mullens.