Coach Todd Haley is getting the most out of the surprising Kansas City Chiefs

The first-place Kansas City Chiefs have surged forward by moving back, coaching quarterback Matt Cassel to take deeper drops that allow him to better survey the field and find his open receivers.

“When you’re back farther like that,” Coach Todd Haley said, “you’re not getting balls knocked down, your offensive line loves you because they don’t have to be perfect, and it increases your margin for error.”

That said, no one could have predicted the latest dropback.

Cassel, in the midst of a spectacular season, underwent an emergency appendectomy Wednesday and is listed as doubtful for Sunday’s game at San Diego. His replacement is Brodie Croyle, who lost each of his nine starts for the Chiefs from 2007 to 2009, albeit surrounded by an inferior supporting cast.

Now comes the most challenging test for the Chiefs (8-4), who have built an NFL-best two-game lead over Oakland and San Diego in the AFC West with four games to play. Can a franchise that won a combined 10 games over the previous three seasons hang on to its division advantage and make it to the playoffs for the first time since 2006?

Regardless of what happens during the next month, however, there’s no denying that Haley has over the first three-quarters of the season established himself as a legitimate coach-of-the-year candidate, along with colleagues such as New England’s Bill Belichick, Atlanta’s Mike Smith, Tampa Bay’s Raheem Morris, Chicago’s Lovie Smith and Rex Ryan of the New York Jets.

“It wasn’t like we had bad players here before, but we didn’t play as a team,” Chiefs outside linebacker Tamba Hali said. “Guys wanted to do their own thing. That’s what Todd saw here. He saw the talent and the potential, but he knew that we didn’t have a team.

“He came in here and changed the way we go about our business, gave us a sense of urgency. It was, ‘If you don’t want to do it, then you don’t want to be here.’”

No one ever accused Haley of having a delicate touch. He was steeped in the hard-edged tradition of the Pittsburgh Steelers — his father, Dick Haley, was the personnel director who assembled the championship Steelers teams of the 1970s — and the younger Haley has shown no hesitation to speak his mind. That was obvious to millions of football fans during the 2008 season, the year before Haley was hired by Kansas City, when he was offensive coordinator of the Arizona Cardinals and they were making a Super Bowl run.

In the fourth quarter of the NFC championship game between Arizona and Philadelphia — which the Cardinals wound up winning — cameras caught Haley and receiver Anquan Boldin angrily screaming at each other. Just another day at the office.

“[Haley] will push you every day and get up in your face, and that’s his coaching style,” former Cardinals quarterback Kurt Warner said. “But he does that so you’ll be the best you can be.”

Warner said as much to the Chiefs’ players last spring during a mini-camp. He accepted Haley’s invitation to talk to the team and share his views on a coach they were only beginning to know.

Recalled Haley: “It was an amazing talk. He said, ‘What do you think of this guy Todd? Kind of a jerk, mean, crazy, yells all the time.’ They were all laughing and he said, ‘That’s what a lot of us thought. But more of us learned pretty quickly that all he wanted was for us to be the best. He was relentless in his pursuit of that.’ ”

That’s something Haley learned from the two most meaningful football mentors in his life, his father and legendary coach Bill Parcells, who worked with both Haleys in the late 1990s as coach of the New York Jets. Dick was the team’s director of player personnel, and Todd made the transition from personnel assistant to coaching, where he went from offensive quality-control assistant to receivers coach.

Parcells said he saw potential in Haley, whom he later hired as receivers coach in Dallas, and he concedes he might have given him an earful of pointed criticism from time to time.

“When you’re a young coach, your sensitivity level is a little higher,” Parcells said. “I can tell you that I was in that same position myself from time to time as a young coach, where there were a few people that were a little rough on me as well.

“But this game is about accountability. Nobody cares why you don’t get the job done.”

Kansas City’s front office and coaching staff is replete with members of the Parcells Jets — coaches and players — who in 1998 were 12-4 and reached the AFC title game before losing to eventual Super Bowl champion Denver. Among those Jets-turned-Chiefs are General Manager Scott Pioli, offensive coordinator Charlie Weis, defensive coordinator Romeo Crennel and offensive line coach Bill Muir, as well as former Jets players who are now coaches: Maurice Carthon, Richie Anderson, Bernie Parmalee, Otis Smith and Anthony Pleasant.

Cassel’s improvement has been dramatic. The same player who had 16 touchdowns and 16 interceptions last season — prompting many Chiefs fans to wonder why the club signed him to a six-year, $63-million deal — has thrown for 23 touchdowns with only four interceptions in the first 12 games. He was sacked 42 times in 2009, tied for fourth-most in the league; this season he’s been sacked 17 times, tied for seventh-fewest. The 2009 Chiefs led the league in dropped passes. This year, the Cassel-to-Dwayne Bowe combination leads the league with 14 touchdowns.

All that is aided, of course, by the Chiefs’ having the league’s No. 1 rushing attack.

Haley made his name in the NFL in part by helping develop All-Pro receivers Keyshawn Johnson and Larry Fitzgerald, among others. Now, Bowe looks to be rounding into that same type of receiver.

Johnson, now an ESPN analyst, said Haley’s “track record speaks for itself.”

“He’s not hard-headed, he listens,” Johnson said. “He pretends to be hard-headed. He wants you to believe that he’s a tough guy. But he’s just like Parcells; behind all that toughness, he’s a little teddy bear. That’s the same way Bill is. Bill’s tough and demanding, but if you do what you’re supposed to do, he’s got a soft spot for you.”

In his second year as head coach, Haley devotes part of his time to offense, yet also makes regular appearances in defensive and special-teams meetings. Having coordinators who have been head coaches — Weis at Notre Dame, Crennel with the Cleveland Browns — he doesn’t need to micromanage.

Haley has played a role, though, in bringing along Cassel. That has included getting him to drop back deeper and quicker — using as a model New Orleans’ Drew Brees, who does it better than any quarterback — and convincing him not to worry so much about looking off receivers. It’s Haley’s belief that in most cases it’s far better to look at a receiver and throw accurately, even if it means tipping the defense to where the ball’s going.

So far, the approach is working. Cassel has had only one interception in the last nine games. Reminded of this, Haley — a coach who knows how fleeting success can be — leaned forward and superstitiously rapped his knuckles on the wooden coffee table in his office.

His mentor, for one, understands that fingers-crossed approach.

“All of us who have been in this game for an extended period of time know that things very seldom go the way you hoped they would,” Parcells said. “When they do go in a positive direction, that’s a very short-lived thing.”

Which is to say, enjoy it while it lasts.

sam.farmer@latimes.com