Running back Joe Mixon agreed to a four-year, $48 million contract extension with the Cincinnati Bengals on Tuesday, according to ESPN's Adam Schefter and NFL Network's Ian Rapoport.

Shortly before the news broke, Mixon dropped a teaser to fans on Twitter:

The 24-year-old, a second-round pick in 2017, was due to hit free agency in 2021. 

Duke Tobin, the Bengals director of player personnel, told 700 WLW's Lance McAlister in May the team was open to discussing a new contract (via Pro Football Talk's Josh Alper):

"Joe's obviously a guy that's shown a lot of ability. He's in a year that he can be extended, and he is a guy that we visited with. We'll go through those discussions and see if there is a fit or a match for a long-term contract with him, obviously a guy we value quite a bit. The great thing about Joe is he goes about it the right way. ... He's the type of guy you want to lock up to a long-term deal. We'll see if we can find the commonality to get that done over time here."

Tobin alluded to the delicate balance NFL teams attempt to strike when working out extensions with their starting running backs. General managers typically want to keep the player around but are wary of committing too much money on the basis that their value could quickly diminish in the years ahead.

Todd Gurley is the most notable example. He signed a four-year extension in July 2018 that included $45 million guaranteed. Not even two full years later, the Los Angeles Rams released him amid concerns about an "arthritic component to his knee."

However, that didn't stop the Carolina Panthers from handing Christian McCaffrey a four-year, $64 million extension that includes almost $38.2 million guaranteed.

While he wasn't in a position to eclipse McCaffrey's record-setting $16 million average annual salary, Mixon's asking price might have gone up based on what the 2019 All-Pro received from the Panthers.

The Athletic's Paul Dehner Jr. reported in April the Bengals were planning for a potential holdout from the Oklahoma product in the absence of a long-term deal.

Following up on the situation in June, Dehner wondered whether the financial ramifications of the COVID-19 pandemic left him stuck in an unenviable position:

"For Mixon and his camp, this will be about understanding his value and figuring out a way to land in whatever guaranteed money he can find. If you still enter this thinking McCaffrey or Elliott in the $15 million per year range is within reason, that will be a non-starter. Half of that is probably a more likely starting point.

"The reality is that teams won't have that type of money to spend on the least valuable position in the game, especially when his leverage is minimal to nonexistent."

Through his first three years, Mixon has looked like a capable every-down back but hasn't enjoyed a true breakthrough.

He ran for 1,168 yards and eight touchdowns while catching 43 passes for 296 yards and one score in 2018. Rather than building on that, he went backward in 2019. Although he eclipsed the 1,000-yard mark again (1,137), his yards per carry fell from 4.9 to 4.1 and he had eight fewer receptions despite appearing in two more games.

Mixon's somewhat underwhelming 2019 could be blamed partially on his supporting cast.

A.J. Green missed the entire season, leaving the Bengals without a viable No. 1 threat in the passing game, while the offensive line ranked 26th in adjusted line yards, per Football Outsiders. Cincinnati selected Alabama offensive tackle Jonah Williams with the No. 11 pick in 2019, only to see him undergo shoulder surgery before playing a single snap.

Now, Green is healthy again and the Bengals fortified the offense through the draft by adding Joe Burrow and Tee Higgins.

To some extent, Mixon could end up regretting signing his extension when he did in the event an improved offense helps lift him to the Pro Bowl.