Michael Smith and Jemele Hill discuss on SC6 why the Steelers decided to give Antonio Brown an extension and explain why his incident did not warrant the team to get rid of him. (2:14)

The Pittsburgh Steelers and Antonio Brown have reached an agreement on a four-year, $68 million extension that makes him the highest-paid wide receiver in the NFL, sources told ESPN's Adam Schefter.

Brown is now tied to the Steelers through the 2021 season. He tweeted after he signed his new deal, which is front-loaded; Brown stands to make less money in the fourth and final year of the extension. The breakdown: Brown will make $18.5 million in the first three years of the contract and $12.5 million in the fourth, sources told Schefter. The deal also includes a $19 million signing bonus.

Antonio Brown signs his new contract, which makes him the highest-paid wide receiver in the NFL. Drew Rosenhaus

The Steelers announced the extension as a five-year deal. Brown's contract for the 2017 season, with a scheduled base salary of $4.7 million, stands as is, the sources told Schefter.

The team had promised to rework Brown's contract this offseason. It restructured his contract in August, advancing $4 million of his 2017 salary into his base salary for 2016.

Brown, 28, is considered one of the best receivers in the league and has been a key piece of the Steelers' offense for the past several seasons. He had one year left on a five-year, $42 million contract he signed in 2012.

A 2010 sixth-round pick out of Central Michigan, Brown has been to five Pro Bowls and has earned three first-team All-Pro nods in his seven seasons. He led the league with 1,698 receiving yards in 2014.

He is the first player in Steelers history to finish with 1,000 receiving yards and 10 receiving touchdowns in three straight seasons.

Brown drew the ire of Steelers coach Mike Tomlin for posting a Facebook Live video from the locker room after a win over the Kansas City Chiefs in the divisional round of the playoffs that caught Tomlin's postgame speech, but the incident appears to have been put to rest.

ESPN's Katherine Terrell contributed to this report.