On Sunday, the Los Angeles Chargers escaped Soldier Field with a 17-16 win over the Chicago Bears to cap a three-game skid. One day later, the Chargers fired offensive coordinator Ken Whisenhunt, ending his second stint with the team after three and a half years.

The Chargers provided little warning for the decision. Head coach Anthony Lynn waited until after his Monday press conference to announce Whisenhunt's firing and did not state a reason for the longtime assistant's ouster in the team's press release. Lynn also declined to name Whisenhunt's replacement, though quarterbacks coach Shane Steichen will step in as the interim offensive play-caller, according to those informed of the situation.

Whether or not Lynn offers his reasons for making the change, the Chargers' offensive performance over the past month offers a window into his thought process.

Under Whisenhunt, the Chargers' rushing attack ground to a halt in October, averaging just 35.5 yards per game and topping out at 39 against the Tennessee Titans in Week 7. In doing so, they became the first team to run for less than 40 yards in four consecutive games since the 1946 season. The lack of production occurred despite the presence of do-everything scatback Austin Ekeler and the late-September return of Pro Bowl running back Melvin Gordon. Even in a pass-first league, the near-complete lack of a ground game must have frustrated Lynn, a former NFL running back.

Whisenhunt also oversaw a similar downturn in the passing game. Quarterback Philip Rivers has thrown for touchdowns on just 3.9 percent of his attempts, the lowest rate of his career as a starter and a drop of 2.4 percentage points from his mark in 2018. Rivers posted just 6.7 yards per pass over his last four games (28th in the NFL during that span) after averaging 8.7 the first month of the season (fourth). The Chargers have also struggled to put the ball into the hands of their playmakers, with Pro Bowl wideout Keenan Allen averaging just 41.3 yards in October after leading the league with 452 receiving yards in September.

Whisenhunt's offense did perform well in one area in 2019: play-action. Rivers posted a quarterback rating of 122.7 on play-action passes while producing zero interceptions and taking just two sacks. In contrast, the veteran signal-caller has a rating of just 87.7 on traditional dropbacks, a figure roughly equal to that of Denver Broncos quarterback Joe Flacco. Likewise, nearly all quarterbacks experience an uptick in efficiency when using play-action with side benefits for the offensive line and running game.

Yet despite the obvious advantages, Whisenhunt used play-action sparingly. The Chargers entered Week 8 tied for the 10th lowest play-action rate in the NFL (21 percent) and never topped 22 percent in any of Whisenhunt's seasons as offensive coordinator. This comes at a time when NFL clubs have collectively incorporated more play-action into their offenses, with five teams calling it more than 30 percent of the time and the Indianapolis Colts pushing 40 percent.

The Thursday before his firing, Whisenhunt offered his reasoning for the low play-action usage:

"Obviously, it's a lot easier to call play-action when you're running the ball effectively. We have had pretty good success this year with play-actions and we haven't run it as effectively at the time. But I just don't think you can live in that world. You can't not have a run game and expect your play-actions to be as efficient."

Whisenhunt's insistence on establishing the run first makes little sense given his admission of play-action's success for the Chargers this year. However, it looks even worse when considering the offense ran on just a third of its plays through the first eight weeks of the season. In the end, Whisenhunt's inability or unwillingness to find a better balance as a play-caller and integrate modern offensive principles cost him his job.

With Whisenhunt out of the picture, the focus now shifts to how the offense will operate with Steichen at the controls. A 34-year-old assistant in his 10th year of coaching, Steichen has never called plays in the NFL. However, he has worked under a variety of offensive coaches — including current Colts offensive coordinator Nick Sirianni — and could bring a more forward-thinking approach to the Chargers offense. Lynn will also have a heavier hand in the play-calling, a change that could lead to lower use of shotgun and a more effective ground game as a result.

Still, Steichen can only alter so much in the middle of the season. The playbook remains the same as it did before his promotion to interim play-caller, as do the players at his disposal. The team still has a 3-5 record with a schedule featuring the Green Bay Packers, Oakland Raiders, Minnesota Vikings, and Kansas City Chiefs.

Whisenhunt might have no longer made sense for the Chargers, but their problems didn't follow him out the door.

-- Jason B. Hirschhorn is an award-winning sports journalist and Pro Football Writers of America member. Follow him on Twitter: @by_JBH