Whisenhunt, the only coach to take the team to the Super Bowl, was relieved of his duties Monday along with six of his assistant coaches and general manager Rod Graves.
Team president Michael Bidwill said he made the decision to remove Whisenhunt and Graves on Sunday night due to the team losing ground in the increasingly competitive NFC West.
"It was a tough decision," Bidwill said. "It felt like, though, after the last three seasons, it was time. It came down to win and losses and the direction we were going as a team.
"You look at the other teams in the NFC West and they were were making dramatic improvements. We felt like this was a move we needed to make to compete at the highest level."
Bidwill said defensive coordinator Ray Horton will be the first candidate interviewed for the head coaching vacancy, and he will also be speaking to Denver Broncos offensive coordinator Mike McCoy and deposed Philadelphia Eagles head coach Andy Reid "in the next several days."
Bidwill said he would also consider college head coaches, but "those are the two (names) I am prepared to share today."
Whisenhunt, 50, had a 45-51 regular-season record with the Cardinals, including a 5-11 mark this season. He led the team to back-to-back NFC West titles in 2008 and 2009 and took them to the Super Bowl following the 2008 season, where they were beaten by the Pittsburgh Steelers.
The shakeup came after three consecutive non-winning, non-playoff seasons. The Cardinals started 4-0 this season but followed that with nine consecutive losses, capped by a 58-0 debacle in Seattle that was the worst defeat in franchise history.
The other coaches who were let go all coached on the offensive side of the ball: Russ Grimm (assistant head coach/offensive line), Mike Miller (offensive coordinator), Chad Grimm (offensive quality control), John McNulty (quarterbacks), Frank Reich (wide receivers) and Tommie Robinson (running backs).
The defensive coaching staff -- including Horton -- remains intact for the time being.
Whisenhunt and Graves each had one year remaining on his contract. Whisenhunt is owed about $5.5 million.
In a statement released by the team, Whisenhunt said he was proud that during his tenure, the team "accomplished some very special and unprecedented things. That’s a testament to the dedication, hard work and talent of so many coaches, players and people throughout the organization.
"But we all understand this business, and when you don’t win enough games changes are made. That doesn’t mean it’s easy, but you definitely don’t have to look far to find people that have it much worse."
Graves joined the team's front office in 1997 and was promoted to general manager in 2007. Steve Keim, the team's vice president of player personnel, will be a candidate to replace Graves, Bidwill said.
Bidwill said he expects to have a "balance of power" between coach and general manager and has no preconceived order in which he will fill the positions.
"If I find the right general manager before the head coach, I'll make that decision," he said. "If it's the right head coach that I find first, I'll make that decision, too. We don't want to pass up the right opportunity."
Whisenhunt, 50, came to the Cardinals after serving as offensive coordinator with the Steelers. In his second season, with veteran quarterback Kurt Warner putting up big numbers, he guided the team on a surprising run to the Super Bowl after sneaking into the playoffs as NFC West champions with a 9-7 record. The Cardinals nearly completed the unlikely march to a championship, but the Steelers rallied in the final minutes for a 27-23 victory.
The Cardinals returned to the playoffs the following year -- losing to the eventual Super Bowl champion New Orleans Saints in the NFC semifinals -- but Warner retired following the season, and inconsistent quarterback play has been a hallmark of the three seasons since.
Matt Leinart, Derek Anderson, Max Hall, Kevin Kolb, John Skelton, Ryan Lindley and Brian Hoyer have all auditioned for the job without lasting success.
Kolb arrived from Philadelphia in a major trade prior to the 2011 season and was signed to a big contract but has been injury-plagued throughout his two seasons while trying to operate behind a suspect offensive line. Both Whisenhunt and Graves were criticized for failing to adequately address the team's needs on the line.
Bidwill said a major topic of conversation in coaching interviews will be identifying, evaluating and developing quarterbacks capable of competing on the highest level, including those currently on the roster.
"I believe that's one of the questions we need to focus on with the candidates," he said. "How do we see about Kevin (Kolb) and his performance and how we can turn him into the quarterback of the future here for the Cardinals and make that decision if he's the right guy. That is a question that needs to be answered, but I'm not ready to give up on Kevin Kolb yet."
With at least seven head coaching vacancies to be filled, the Cardinals could face vigorous competition for their next head coach. While Bidwill said there's always a sense or urgency, regardless of how many vacancies are to be filled, the realities of the holiday season and the upcoming playoffs mean "it's not going to happen at lightning speed."