Chip Kelly has been the 49ers‘ head coach for less than 100 hours, but you already might have heard this question 100 times: How can this man co-exist with general manager Trent Baalke?

In Philadelphia, where his firing was more about his personality than ability, Kelly didn’t see eye-to-eye with, among others, Eagles executive Howie Roseman. And Baalke couldn’t make it work with the franchise’s last hard-driving, hard-to-get-along-with head coach, Jim Harbaugh.

Baalke will retain personnel control, which Kelly wielded last year with the Eagles. So, again, how will two controlling Type As with unpolished interpersonal skills get along as they reshape the 49ers’ roster?

The answer: perhaps far better than many might think.

Peter Earl McCollough/Special to the Chronicle

As it turns out, Kelly and Baalke share a philosophy when it comes to evaluating players, which is their most obvious potential source of friction. They both prize size and their might-is-right philosophy has been shaped by Hall of Famer Bill Parcells, whose teams were more about physicality than finesse.

In Philadelphia, Kelly often offered a variation of this quote: “We want taller, longer people because bigger people beat up little people.”

Baalke, a man obsessed with draft prospects’ arm length, routinely has offered his spin on the same theme: “‘Big’ wins,” Baalke said during the 2014 draft. “‘Big’ wins a lot of football games in the league.”

Baalke’s mentor is Parcells, 74, whom Baalke attempted to hire before the 49ers landed Harbaugh in 2011. Baalke entered the NFL in 1998 as a scout with the Jets when Parcells was the head coach, and Baalke consulted with the two-time Super Bowl winner during the 49ers’ recent coaching search.

For his part, Kelly’s philosophy was at least partly shaped by Alabama head coach Nick Saban, who is part of the Parcells coaching tree.

Kelly visited Saban in Tuscaloosa, Ala., this month before the Tide’s win in the national-championship game. Kelly also visited with Alabama offensive coordinator Lane Kiffin before the 2014 Sugar Bowl. Saban, who has won five national titles, has termed Kelly a “good friend.”

Saban spent four seasons (1991-94) as the Browns’ defensive coordinator under Bill Belichick, who was the Giants’ defensive coordinator for six seasons (1985-90) under Parcells. In 2012, at an Alabama coaching clinic, Parcells was the guest speaker. In introducing Parcells, Saban noted his influence on Alabama’s program.

“There’s always a few guys that are mentors to you in terms of how you want to do things, what you want to do,” Saban said. “And, indirectly, because of my association with Bill Belichick, who worked with Bill Parcells for years … I learned a lot of (Parcells’) philosophy. And our teams reflect his philosophy. How we recruit players reflects his philosophy.”

That Parcells-inspired recruiting philosophy was followed by Ed Marynowitz, who was Alabama’s director of player personnel from 2008 through ’11. Marynowitz arrived in Alabama after spending a season as a Dolphins scouting assistant under Miami’s executive vice president of football operations … Bill Parcells.

Last year, after Kelly assumed general-manager power in Philadelphia, he promoted Marynowitz (previously the assistant director of player personnel) and made him his right-hand man in the personnel department.

Before the 2015 draft, Marynowitz — who was fired when Kelly was dismissed in December — said he shared Kelly’s big-is-better mind-set. He also revealed Kelly’s oft-repeated quote wasn’t original.

“Size-speed wins, No. 1,” Marynowitz said. Kelly has “used the same line Nick Saban has used: Big people beat up little people. There’s a reason the heavyweights don’t fight the lightweights. This is a big man’s game.”

And the Eagles’ moves during Kelly’s tenure reflected that mind-set.

In 2014, for example, they released wide receiver DeSean Jackson (5-foot-10, 178 pounds), drafted wide receiver Jordan Matthews (6-3, 212) in the second round and signed wide receiver Riley Cooper (6-4, 230) to a five-year contract extension. In 2015, Kelly signed running backs DeMarco Murray (6-0, 217) and Ryan Mathews (6-0, 220), both of whom are bigger than LeSean McCoy (5-11, 208), who was traded to the Bills.

Last year, two of the Eagles’ top three cornerbacks — Byron Maxwell and Nolan Carroll — were each 6-1. And their starting outside linebackers — Connor Barwin and Brandon Graham — each weighed at least 264 pounds.

Marynowitz said his background with Parcells and Saban made him a good match with Kelly.

“I came from a similar school of thought,” Marynowitz said last year. “I’ve always been around prototype-driven personnel operations. Defer to size and speed and try to get guys that look the same and have a similar skill set.”

A week after Marynowitz spoke with reporters, the 49ers used their first-round pick on Arik Armstead, a 6-7, 292-pound behemoth who was the tallest defensive lineman at the NFL combine.

Would Kelly and Baalke have seen eye-to-eye on that pick?

Probably. Armstead played at Oregon, where he spent his first season with the head coach who recruited him: Chip Kelly.

Eric Branch is a San Francisco Chronicle staff writer. E-mail: ebranch@sfchronicle.com Twitter: @Eric_Branch