Before joining the San Francisco 49ers in February, defensive coordinator Robert Saleh spent three seasons as the linebackers coach for the Jacksonville Jaguars. On Sunday, he will go against his former team for the first time.

On Wednesday, 49ers head coach Kyle Shanahan previewed the matchup against the Jaguars. On Thursday afternoon, Saleh spoke to reporters about the reunion at Levi's Stadium.

The Jaguars defense has enjoyed a great deal of success this season. It is ranked first in points and passing yards allowed and third in total yards allowed. Saleh is proud of his former unit.

"You know what? I'm pumped up for those guys," Saleh said. "There's so many people there that were there for the last three years. So, really excited to see those guys have the success that they're having. It's a tribute to guys like [Jaguars general manager] Dave Caldwell, [Jaguars director of player personnel] Chris Polian, [Los Angeles Chargers defensive coordinator] Gus Bradley and all them who were there from the beginning and tore that thing down and brought it back up to what it is.

"All the hard work that those guys have put in over the last four years, they're really starting to reap the benefits of their hard work. It's really cool to see it happen."

Saleh discussed the challenge of going against the NFL's top run offense on Sunday, which is led by rookie running back Leonard Fournette, who the defensive coordinator said moves like he's 200 pounds and hits like he's 250 pounds.

"Every week presents a new challenge," Saleh said. "It's the number one run offense in all of football. It's not just because they run the ball over and over again and they have opportunities to run. I think they're sixth in yards per carry. They get after it in the run game. They're very physical in the run game. They don't try to trick you, which I respect a lot.

"You don't know exactly what they're going to do run-game wise, but they've got conviction in what they are in the run game, and they line up and they try to move the pile on the line of scrimmage. So, I've got a lot of respect for the run game and what they've been doing."

The Jaguars run a similar defense to the 49ers, so the question came up whether or not Shanahan, who runs the San Francisco offense, has come to him for insight on facing his former unit.

"Kyle and his staff, they're coming from Atlanta who pretty much runs the same scheme too," Saleh said. "They might ask a question or two, but I think they're pretty well aware of all the things that we do defensively and all the techniques that we teach. So, a question here and there, but they're not relying on me."

The 49ers defensive coaching staff will be scheming to stop Jaguars quarterback Blake Bortles, who was the third overall pick during Saleh's first year with the Jaguars. What does Saleh think about the season Bortles is having?

"It seems to me like Blake is playing with a tremendous amount of confidence," Saleh said. "He's thrown darts. He looks very accurate, he's mobile, he's tall in the pocket, he looks lean, and he looks in shape. He looks fantastic, to be honest with you. I'm not trying to sugarcoat anything. He looks really, really good."

Saleh was asked about Bortles' targets in the passing game and how the offensive weapons have helped the quarterback.

"Blake is putting the ball where only his receivers can catch it," Saleh said. "He's throwing the ball really, really well right now. His receivers are running really good routes. You watch that Houston game, guys were running wide open and Blake was hitting them in stride.

"It's been a combination of the way [Jaguars offensive coordinator Nate Hackett] has been calling his games and scheming up, a combination of how you can include the O-Line and the way that they've been protecting. And, Blake is standing back there playing with great confidence. It's a little bit of everything.

"They're young guys, so there's not a lot of tape on them, but they're stepping up, and they're answering the bell. They're very capable, obviously capable receivers. You never want to crown a rookie quite yet, but you can tell there's great potential within that group. "

As for the defense, cornerback Jalen Ramsey was the Jaguars' fifth-overall draft pick in 2016, and he is half of that starting cornerback duo that helped the Jacksonville defense become the top unit against the pass.

"The one thing that makes Jalen tick is his mindset," Saleh said. "He is a freak athlete, he's got freakish length, he's got freakish size, but what makes him special is he's a flat dog on the football field, and he doesn't play out of control. If you let him, he'll try to embarrass you. That's what I like most about the guy.

"There's a reason why he was a top-five pick. There's not many like him. He's got a chance to be special if he continues with that mindset."