ALAMEDA -- Denver Broncos coach John Fox, having been there before, realized early on his defensive coordinator had the look of one-and-done.
As coach of the Carolina Panthers, Fox hired Jack Del Rio in 2002, only to lose him after one season when the Jacksonville Jaguars hired Del Rio as their head coach.
So when the St. Louis Rams and then the Raiders came calling for Dennis Allen after a single season as the Broncos defensive coordinator, Fox expected it.
"He's a guy with I call the 'it' factor," Fox told Bay Area reporters by conference call. "So it did not surprise me people looking for coaches in this league would be interested in talking to him."
After Allen was offered the Raiders head coaching job by Reggie McKenzie, he leaned on Fox for advice.
"He said go there and you'll do a great job, and you're ready for the job," Allen said. "I've talked to him since then, and he doesn't give me all his secrets, but he's helped me out a lot."
Allen will line up across the field from Fox when the Raiders visit the Broncos Sunday at Invesco Field.
Under Allen, the Denver defense went from 32nd overall to 20th and from 30th in rushing to 22nd. Fox, a defensive coach, gave Allen the responsibility to be the defensive play-caller, the same way Allen has done with Raiders defensive coordinator Jason Tarver.
"He's not afraid to make tough decisions," Allen said. "He believes in a lot of the same things I believe in. He's always had a tough, smart, disciplined team and I believe in those things.:
Allen watched with admiration last season as the offensive staff changed the Broncos' entire offensive approach on the fly to accommodate Tim Tebow, with the end result an AFC West title.
Denver cornerback Champ Bailey said he expects the Raiders defense to be very well prepared.
"He had this thing where he would break down personnel formations," Bailey told reporters in Denver. "He was really big on how teams broke down and how they came out of the huddle. Read the story. They're telling you something when they come out and line up so you know what to expect.''
Cornerback Tracy Porter came to Denver as a free agent this season but had Allen as his defensive backfield coach in New Orleans.
"He stayed on me more than anything about finishing plays," Porter said. "He taught me to play within myself, don't try to do anything out of the realm. He believed in me and gave me more confidence week in and week out for them to put me out there.''
Porter said he and his Saints teammates talked often about how Allen would move on to be a defensive coordinator "pretty soon, and we said it wouldn't shock us if he became a head coach.''
Denver defensive end Elvis Dumervil said he hadn't really thought in terms of Allen as a head coach but liked the fact he always knew where he stood.
It's a sentiment that has been echoed by several Raiders players.
"Just his attitude, the way he comes to work. Consistency," Dumervil said. "There's a lot you can learn from a guy like that."