San Francisco's D.J. Jones proposes to his girlfriend on the field before the 49ers take on the Browns on Monday Night Football. (0:28)

SANTA CLARA, Calif. -- As he prepared to surprise his girlfriend with a pregame proposal, San Francisco 49ers defensive tackle D.J. Jones enlisted the help of the person in the organization with the most fitting job for such a task.

Austin Moss II, whose official title is 49ers Director of Player Engagement, helped Jones in the planning and execution of what Jones would later call one of the three best days of his life as he got engaged to girlfriend-turned-fiancée, Kayla Fannin, about an hour and a half before Monday night's 31-3 drubbing of the Cleveland Browns.

Surrounded by friends, teammates and family on the 49ers' sideline at Levi's Stadium, Jones pointed across the field in an effort to distract Fannin.

When Fannin turned back around, Jones was on one knee proposing marriage. A surprised Fannin briefly gathered herself before saying "yes" as Jones' family cheered for the couple.

"She had no idea [the proposal was coming]," Jones said. "I saw it in her face. She started crying instantly. It's pretty cool."

The 49ers broadcast the proposal on the stadium video board and later shared the full video on Twitter.

Jones, who met Fannin through his sister and had been dating her for about two years, said the proposal idea actually came to him about two weeks ago, though he had been pondering marriage for much longer.

Once he settled on the pregame sideline idea, he asked Moss for some help. So, when Fannin and his family arrived Monday night, Moss met them in the greeting area, walked them to the field and escorted them to the sideline.

From there, Jones, Fannin and Jones' family posed for a photo, setting the stage for Jones, who admitted he was "a little" nervous to pop the question.

"I think she asked, 'Why are we here?'" Jones said. "And I was like 'You don't know why we're here? And I pointed over her shoulder and she just turned and I popped down."

A tearful and happy Fannin said "yes," and Jones and the Niners proceeded to roll over the Browns to begin the season 4-0 for the first time since 1990. After the game, Jones said it was one of the three happiest days of his life, ranking it next to the day he was drafted and a day he left open in case he couldn't think of the real answer at the moment.

"I love her to death," Jones said. "I love the game of football, and going 4-0 on Monday night is pretty cool in my book."

The Niners also posted video of receiver Marquise Goodwin celebrating after the proposal.

Congrats fam 👏 pic.twitter.com/BuVeuYsKaK — San Francisco 49ers (@49ers) October 7, 2019

Jones, a sixth-round pick in 2017 out of Mississippi, has started the first three games for the 49ers at nose tackle.