JACKSONVILLE, Fla. -- Jacksonville Jaguars coach Doug Marrone doesn't want to talk about his short stint with -- and abrupt departure from -- the Buffalo Bills in advance of the teams' matchup Sunday in the first round of the playoffs.

That's not only a waste of time, he said, but also irresponsible and a disservice to his assistant coaches and players.

"What's past is past," Marrone said Monday. "I'll tell you guys the truth. ... This stuff happened so long ago, OK? There's obviously been a lot of stuff out there. That stuff is done. It's over. I can't put it any simpler than that. So I'm not going to take away my primary responsibility to look back on a situation that occurred, what, three years ago.

"If I do that, then I shouldn't be the coach of the Jacksonville Jaguars."

Marrone spent two seasons as the head coach in Buffalo and led the Bills to a 9-7 record in 2014, their first winning season in a decade. He then opted out of his contract because of uncertainty over possible organizational changes after the team was purchased by Terry and Kim Pegula following founder Ralph Wilson's death.

The clause in his contract that allowed Marrone to do that also guaranteed his $4 million salary in 2015, which he collected even after being hired as the Jaguars' offensive line coach roughly a month after his resignation.

Marrone became the Jaguars' interim head coach after Gus Bradley was fired on Dec. 18, 2016, and he was hired permanently on Jan. 9. He guided the Jaguars to a 10-6 record and an AFC South title this season, the franchise's first division championship since 1999.

The Jaguars will play host to the Bills on Sunday at EverBank Field in Jacksonville's first playoff appearance since 2007. So, naturally, Marrone's short-but-complicated history with the Bills is a huge subject this week -- but not for Marrone.

"My job is to make sure that I do the best job for this team," Marrone said. "Hey, listen, am I happy that [Buffalo snapped its 18-year playoff drought]? I am. I am. I'm happy for their fans and I'm happy for the organization, as well as I am for the other 11 teams, or 10 teams that are in it, but my focus is on our fans, our team, and where we want to go.

"It's going to be a week of people trying to pull that apart, and I'm not going to let that happen because of what my job is."

Marrone admitted at the NFL scouting combine last March that he did make some mistakes during his Bills tenure. He said he spoke with Terry Pegula but wants to keep that conversation private.

"When you look back, I'll be honest, there's some things that I should've done differently," Marrone said at the combine, "and I think I've learned from that and it's made me a better coach today."

While Marrone wouldn't say Sunday's playoff game had any special meaning, nose tackle Marcell Dareus did. Buffalo drafted Dareus third overall in 2011 and he spent the first 6½ seasons of his career there -- making the Pro Bowl under Marrone in 2013 and 2014 -- before being traded to the Jaguars for a sixth-round pick on Oct. 28.

This weekend's matchup is definitely personal for him.

"It's hard to say it isn't," Dareus said. "I'm just happy for the opportunity, man. It's just crazy. God is funny. Just don't question his work. Just do your job.

"They [Buffalo] had to make a move, and it's business, but you can't act like it doesn't hurt [to be traded for a sixth-round pick]."

Dareus said he received 170 text messages from friends, family and former Bills teammates on Sunday night after the Jaguars-Bills matchup was set. He called it ironic that his former and current teams both snapped playoff droughts and will play each other, but he also said he was happy for his former teammates.

"It's pretty funny," said Dareus, who recorded his first sack as a member of the Jaguars during their 15-10 loss at Tennessee on Sunday. "We're all laughing about it, all my friends back there and everyone here. It's comical almost."