Caldwell and Mularkey spent four years together in Atlanta, getting to know each other well enough that Caldwell didn't need a sit down with Mularkey after he got the GM job Tuesday.
"It was tough," Caldwell said. "I have a ton of respect for Mike. ... It's never easy and that's probably the worst part of the business."
Potential replacements for Mularkey include former Chicago Bears coach Lovie Smith, Indianapolis Colts offensive coordinator Bruce Arians, St. Louis Rams offensive coordinator Brian Schottenheimer and San Francisco 49ers offensive coordinator Greg Roman.
Schottenheimer was up for the Jacksonville job last season, and Roman has been linked to the Jaguars since Caldwell became the leading candidate to replace Smith.
Roman and Caldwell were teammates and roommates in the 1990's while attending John Carroll University.
"I think Greg is a heck of a coach," Caldwell said.
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