Numerous reports have pegged Ken Whisenhunt as the next head coach of the Detroit Lions. But according to NFL rules,  the 51-year-old San Diego Chargers offensive coordinator will have to wait until the his current team’s postseason run is over until he can be officially hired.

The Chargers are fresh off a 27-10 blowout win over Cincinnati in the AFC wild card round, and next take on Denver at Mile High on Sunday.

While it appears Detroit has its heart set on Whisenhunt, there is still plenty of time for another candidate to emerge. According to the Detroit Free Press, teams can conduct a first interview of assistants whose teams are currently in the playoffs ahead of the divisional round. If permitted a second interview, a candidate can also meet in the weeks leading up to the conference championships and Super Bowl.

The Free-Press also reported that Detroit will bring Whisenhunt in for a second interview this week, with Chargers first-year head coach Mike McCoy allowing any and all of his assistants to seek other opportunities.

The Lions aren’t taking any chances and are still vetting and interviewing top assistants, including the Ravens offensive coordinator Jim Caldwell, and recently fired Tennessee Titans head coach Mike Munchak. All three will need a plan to bring quarterback Matthew Stafford back to his 2011 form.

Since reaching career-highs in completion percentage (63.5), passing yards (5,038), touchdowns (41), and yards per attempt (7.6), Stafford has seen his numbers decline in each category and the Lions have gone 11-21. Clearly Detroit already has the talent in place, but needs guidance. The thinking is with the right coach Stafford, All-Pro receiver Calvin Johnson, and running back Reggie Bush can make deep postseason runs over the next half decade

Whisenhunt has proven he can take a moribund and talent-limited franchise, and sculpt into a contender before. In his first three years as Arizona’s head coach, Whisenhunt led the team to two NFC West titles and a near Super Bowl victory. It was just the second time in the franchise’s history it reached the playoffs in consecutive years.

Other than Whisenhunt, Caldwell is the only other coach to have formally met with Lions officials. Largely responsible for revamping Baltimore’s offense for their stretch Super Bowl run last season, Caldwell has more than 13 years of NFL experience and has specifically worked with quarterbacks throughout his career.

Caldwell arrive in Indianapolis in 2002. A year earlier Peyton Manning and the Colts had gone 6-10 and the typically careful quarterback had tossed 23 interceptions, the second-worst mark of his career to present date. Over the next nine seasons Manning would win all four of his MVP awards and a Super Bowl.

According to a report from ESPN, Munchak is scheduled to interview on Friday less than a week after the Titans let him go due to his unwillingness to fire several of his assistants. Tennessee even reportedly offered Munchak a hefty contract extension and raise, but he wouldn’t budge.

After 12 seasons with the franchise when it was known as the Houston Oilers, Munchak worked up the coaching ladder for the next 16 years and eventually took over for Jeff Fisher in the 2010. His overall record of 22-26 might not have much luster, but Munchak and the Titans were poised for a breakout season until quarterback Jake Locker went down with shoulder and hip injuries.

Munchak has also been tied to the vacancy at his alma mater Penn State.

Other freshly available candidates include Bengals offensive coordinator Jay Gruden and defensive coordinator Mike Zimmer, and San Francisco offensive coordinator Greg Roman, according to the Free-Press. Gruden and Zimmer can be hired immediately with Cincinnati’s postseason cut short.