SANTA CLARA — In the pantheon of congratulatory phone calls after a win, there's the President of the United States' following a Super Bowl, and there's the one from your 100-year-old grandmother once you beat a division rival.

Kevin McDermott loved the call he had after Sunday's 19-17 49ers victory over the Seattle Seahawks.

Shortly after snapping the ball on Phil Dawson's last-minute field goal, McDermott was on the line with his grandmother, Opal, who celebrated her 100th birthday only three days earlier.

"Great job," his grandmother told him from a family gathering in Portland, Ore.

"Happy birthday," replied the 49ers' rookie long snapper.

McDermott has gone virtually unnoticed in first NFL season, and that's always the best-case scenario for a long snapper. Watching from afar has been his grandmother, who lives in South Dakota, and used to publish the Highmore Herald newspaper with her husband, William.

"She watches my games and knows what's going on," McDermott said. "She's a pretty unbelievable lady. She takes care of herself. ... The only thing she really can't do is drive because of her eyesight. Other than that, she's 100 percent capable."

When she turned 100, Opal McDermott's grandson posted a picture on Twitter of her playfully sitting with a cigar in her mouth and a bottle of Fireball liquor in her hands. The picture has been retweeted over 300 times.

McDermott was picture-perfect himself against the Seahawks. He passed his biggest test of his rookie year with a flawless delivery to holder Andy Lee for Dawson's game-winning kick.

"That was good, to get the feel of a high-intensity, high-pressure game," said McDermott, noting he approached that snap as "just like practice."

Said Lee: "Me and Phil were just watching film with him and asked, 'Were you nervous on the game-winning snap?' He's like, 'No.' ... He's done a great job. I don't even worry about him. That's what I want."

After training camp, the 49ers decided upon McDermott, an undrafted rookie out of UCLA, as a capable replacement for Brian Jennings, a 13-year veteran and two-time Pro Bowler.

After only catching snaps from Jennings since 2004, Lee has adjusted to McDermott just fine, and that goes in the punting department, too. Lee ranks second in the league with a net average of 42.6 yards per punt.

"The biggest compliment I can give him is I don't have to worry about him," Lee said. "Knowing that the ball's going to be there, knowing that he's going to do his job, that's the biggest thing."

Dawson's winning kick marked the 20th consecutive field-goal attempt he's made, an ongoing franchise record.

McDermott remains humble, insisting: "I'm still a rookie. I don't deserve to be given anything. I had to work to get here. I have to keep working to stay here."

To better understand what his work entails, consider the scenario for his last snap. The 49ers trailed their bitter rival by a point. They had just marched down field with the help of two key runs by Frank Gore and Anquan Boldin. They only needed Dawson to kick a 22-yarder over a Seahawks unit that included Red Bryant, who blocked a field-goal attempt last season that Richard Sherman returned for a tone-setting touchdown in a 42-13 rout of the 49ers.

Where was Red Bryant lined up this time?

Said McDermott: "To be honest, I wasn't paying attention. With my job, I'm looking between my legs, backward."

For more on the 49ers, see Cam Inman's Hot Read blog at blogs.mercurynews.com/49ers. Follow him on Twitter at twitter.com/CamInman.