One week after he skipped voluntary workouts, Pittsburgh Steelers wide receiver Antonio Brown showed up Monday to join his teammates.

The Steelers tweeted photos from Monday's workout session that included Brown.

"I'm not into hypotheticals," coach Mike Tomlin said Monday when asked about the reasons for Brown's absence last week. "We had a good day today. He was in the group today so I'll leave it at that."

A source told ESPN last Tuesday that Brown wasn't attending workouts as he is seeking a new contract. The All-Pro has three years left on a five-year, $42.5 million extension he signed in 2012.

Brown, who will turn 27 in July, made a base salary of $6 million in 2014. The three-time Pro Bowler is due a base salary of $6 million this year, $8.25 million in 2016 and $8.71 million in 2017.

Offseason workouts and most of the practices, which begin for the Steelers in late May, are voluntary. The three-day minicamp that the Steelers will hold June 16-18 is mandatory for all players. The minicamp is the only offseason activity for which Brown could be fined for missing.

The Steelers typically don't re-sign players to new contracts until they are going into the final year of their deal. They make an exception with starting quarterbacks; the Steelers usually sign those players with two years left on their contracts.

Pittsburgh has not had a significant training camp holdout since wide receiver Hines Ward in 2005. Ward missed the first two weeks of camp over unhappiness with his deal, which had one year and $1.66 million left on it.

Brown set a number of Steelers records in 2014, including most touchdown receptions (13) in a season. He also led the NFL in a handful of categories, including receptions for first downs (85) and third-down catches (36).

He has 5,259 receiving yards in five seasons and also returns punts. He is sixth on the Steelers' career receiving yards list, 203 yards behind Hall of Famer Lynn Swann for fifth.

Brown is fourth on the Steelers' career receptions list with 390.

Scott Brown of ESPN.com contributed to this report.