John Middlekauff isn’t just any sports-talk radio host yammering about Chip Kelly, the new 49ers coach. Middlekauff worked as a Philadelphia Eagles scout when Kelly arrived there in 2013 for his first NFL coaching gig.

“He has position-specific stuff he looks for in a player,” said Middlekauff, who co-hosts “Haberman & Middlekauff” on 95.7 The Game weekdays from 10 a.m. to noon.

Before Middlekauff’s three years as an Eagles scout ended after the 2013 draft, he captured the essence of Kelly’s preferences and methods, which Middlekauff also gleaned through in-season visits to the University of Oregon, Kelly’s previous stop.

“He’s very, very good on game day, he’s excellent on coaching quarterbacks, and he doesn’t do anything on defense,” Middlekauff said. “And it’s not easy to play defense for him because you’re on the field more.”

The 49ers hired Kelly on Thursday, and his introductory news conference likely won’t be until this Wednesday or Thursday, a delay attributed to his focus on first compiling a staff. Eric Mangini, this season’s defensive coordinator, is a “strong possibility” to remain in that role, Fox Sports reported Monday.

“His defensive coordinator is so important,” Middlekauff said. “He missed out on some guys in Philly. If they don’t have a defensive coordinator by the (introductory) press conference, then what have they been doing?”

Mangini would be one of the few holdovers from former coach Jim Tomsula’s staff, and the 49ers will be looking to improve their rankings of 18th in points allowed and 29th in yards allowed.

“The (fast) tempo, it doesn’t benefit (the defense),” Middlekauff said. “For an innovative guy, he has stubborn tendencies. Any game, they look the same.”

Kelly delivered 10-6 records his first two years with the Eagles, including a wild-card playoff loss his debut season. After assuming personnel control in 2015 and making a slew of controversial moves, Kelly had the Eagles at 6-9 when he got fired before this season’s final game.

Count Middlekauff among those curious to see how Kelly works with maligned quarterback Colin Kaepernick. “(Kelly) was big on accuracy and decision making,” Middlekauff said. “Those two things, for Colin, are in the weakness category.”

Beside quarterbacks, running backs also draw much of Kelly’s attention, and he prefers multiple, top-level rushers, said Middlekauff, noting that Jarryd Hayne will have to take advantage of a heavier workload in the offseason to be a legitimate backup next season to Carlos Hyde and others.

“There will be three times as many reps in OTAs or camps, and Jarryd will get so much work that maybe he can exponentially improve more than he would in any other offseason program,” Middlekauff said. “This is a best-case scenario for Jarryd Hayne in terms of improving.”

Middlekauff depicted 49ers left tackle Joe Staley as Kelly’s “ideal player,” citing his athleticism, professionalism and work ethic. The non-ideal player: one who draws attention to himself via social media, has foolish behavior on or off the field or shuts himself off from teammates.

“The moment he sniffs out a red flag, whether a guy got suspended in college or did something most people would look past in the draft, he refused to touch it,” Middlekauff said. “He got burned too many times at Oregon and realized it wasn’t worth it.”

Defensively, Middlekauff sees Kelly and 49ers general manager Trent Baalke sharing a common vision, in that both believe in tall, long-armed pass rushers in a 3-4 scheme (see: Arik Armstead) with bigger cornerbacks (see: Dontae Johnson).

For more on the 49ers, see Cam Inman’s Hot Read blog at blogs.mercurynews.com/49ers.