Kliff Kingsbury was a season into his NFL career – at that point, as a quarterback coming off a missed-from-injury rookie season – with the Patriots when Matt Patricia first showed up in New England in 2004.

Kingsbury had been helping break down video for coaches after he had been hurt, and Patricia, only four years older than Kingsbury and hired as an entry-level offensive quality control coach by head coach Bill Belichick, was also charged with such duties.

"We were all kind of in the foxhole together," Patricia said during a conference call Tuesday.

Kingsbury's time with the Patriots, alongside Patricia, soon ended when Kingsbury was released at the end of the 2004 preseason. But those days are still in the memory banks of the now-head coaches of the Cardinals and Lions, respectively, as they prepare to meet in Sunday's regular-season opener at State Farm Stadium.

"I've always been impressed by how smart he is, how hard of a worker he is," Kingsbury said. "You can see he's trying to build it that way, and he's definitely putting that defense together in that mindset."

Patricia was helping with the offensive line in those early Patriot days; Kingsbury and fellow QB Rohan Davey (himself a one-time Cardinal as well) were trying to help with whatever they could on offense.

"It was pretty cool, actually, to watch them go in there and watch them do the stuff that a lot of the coaches were doing, especially with Kliff knowing that that would be his future profession," Patricia said, an interesting comment given that Kingsbury has insisted he had no plans to eventually coach during his playing days.

Their teams meeting, especially in the opener when Kingsbury hasn't coached on this level, brings a level of intrigue. Kingsbury is considered an offensive savant. Patricia, meanwhile, "is one of the brightest minds in football," Kingsbury said.

"He's like a nuclear physicist or something, right?" Kingsbury added. "He graduated from one of those engineering schools."

Patricia did graduate from Rensselaer Polytechnic Institute, studying aeronautical engineering. He could've done well in that line of work, but instead chose to climb the coaching ladder, spending more than a decade with the Patriots before becoming the Lions coach last year.

"Just to see where he started, (and) at that place (with the Patriots) you earn your stripes," Kingsbury said. "He worked his way up and helped them win a bunch of championships, and now he's trying to do that on his own."

Patricia's smarts will be tested in trying to anticipate what the Cardinals might do with rookie quarterback Kyler Murray. The Cardinals showed little of their actual playbook in the preseason; the Lions have countered by studying deep into Kingsbury's coaching past.

Whether Patricia would be able to glean anything from his short time with Kingsbury is unlikely. Fifteen years is a long time, especially when Kingsbury wasn't actually coaching yet and Patricia was just trying to figure out the gig on the NFL level.

But Patricia said it was obvious Kingsbury digested well the game of football. Maybe coaching was inevitable.

"I just think that he really understood concepts, he understood situational football and he was able to put his mindset and mentality into those situations and really be able to understand the things that he was trying to do," Patricia said. "A lot of it from a quarterback position, you have to have to look at the game from different perspectives of concepts, down-and-distance and game clock management and all the rest of that.

"He just could really handle all of that at a high level, which is pretty unique."