Second-year RBs pace Dolphins, Chargers

Two of the top young running backs in the NFL will share the field in San Diego on Sunday.

And both players were considered huge question marks entering the season after disappointing rookie campaigns.

San Diego's Melvin Gordon is finally living up to his star billing, while Miami's Jay Ajayi came out of nowhere to become one of the NFL's top rushers. Those developments add plenty of luster to Sunday's matchup (4:05 p.m. ET, CBS) between the Chargers (4-5) and Dolphins (4-4).

Gordon is coming off the top game of his career, a 196-yard rushing effort against the Tennessee Titans that boosted him to third in the NFL with 768 yards. He also leads the league with 11 touchdowns (nine rushing, two receiving) after failing to find the end zone as a rookie.

Ajayi is in the midst of a superb three-game frenzy in which he has rushed for 529 yards, a stretch that saw him become just the fourth player in NFL history to post back-to-back 200-yard outings. He ranks sixth in the NFL with 646 rushing yards and is averaging a sparkling 6.0 yards per carry.

Turns out the two 23-year-olds have a close friendship, stemming from working out together prior to the 2015 NFL Draft.

"I'm always checking on Melvin every week to see how he does," Ajayi said. "I'm so proud of him to come back from last year, where he wasn't able to score a touchdown and a lot of people were kind of starting to write him off a little bit.

"Through talking with him through the offseason and everything, he really put his head down and did a lot of things to set himself up for a great year. He's starting to showcase the ability that everyone knew he had, and it's exciting to see how well he has been doing."

Gordon's rushing output against Tennessee was the ninth most in Chargers history, and he added 65 receiving yards to give him 261 total yards.

He already has passed last season's total of 641 rushing yards. Gordon also has erased last season's image as a fumbler -- he lost four of the five he put on the ground -- and coach Mike McCoy now repeatedly refers to him as the team's "bell cow."

"Every guy wants to make a play," Gordon said. "Every guy wants you to look at him and think, 'I can count on this guy.' That's how we all want to be. When you get the opportunity to have the ball in your hands, it's your job to make something happen."

Ajayi is making things happen as well after opening the season as a healthy inactive against the Seattle Seahawks. Arian Foster's injury issues -- and eventual retirement -- opened the door for Ajayi, who responded with outings of 204 yards against the Pittsburgh Steelers, 214 versus the Buffalo Bills and 111 against the New York Jets during the club's three-game winning streak.

The play of rookie left guard Laremy Tunsil helped fuel Miami's rushing success. Getting Ajayi loose could be a challenge on Sunday with San Diego ranking fifth in the NFL in rushing defense at 85.3 yards per game.

Rookie defensive end Joey Bosa is making an impact on the Chargers' defense, as he has four sacks in five games. Cornerback Casey Hayward, tied for the NFL interceptions lead with five, and outside linebacker Melvin Ingram, who has a team-high five sacks, also are enjoying standout seasons.

San Diego quarterback Philip Rivers is feeding off the improved run game, throwing for 2,560 yards and 17 touchdowns against seven interceptions.

Dolphins quarterback Ryan Tannehill is experiencing a relatively quiet campaign by passing for 1,877 yards and eight touchdowns against seven interceptions. He has passed for just 605 yards during the three-game winning streak that has been highlighted by Ajayi's emergence.

Miami ranks just 30th in defending the run (136.1 yards per game) despite the presence of defensive tackle Ndamukong Suh. Veteran defensive end Cameron Wake has a team-best five sacks, including four in the past three games.

The contest also marks the first time that McCoy and Miami's Adam Gase will square off as head coaches. The two spent four years together on the Denver Broncos' staff before McCoy became the Chargers' coach in 2013.

Another backdrop is that the contest is San Diego's first at Qualcomm Stadium since the city's voters overwhelmingly said no to a ballot measure to fund a $1.8 billion downtown stadium. The franchise's future home is once again in limbo.

"As you can imagine, we're all disappointed," Rivers said. "In the midst of a season, you can't get too caught up in it."

Rivers passed for 311 yards and three touchdown passes last December when the Chargers sailed to a 30-14 victory over the Dolphins.