SANTA CLARA, Calif. -- The NFL suspended San Francisco 49ers wide receiver Jerome Simpson on Tuesday without pay for the first six games of the season for violations of the league's substance-abuse policy.

The 49ers were aware of a likely suspension for Simpson for previous issues, but nothing that is known to have occurred since he joined the 49ers on a two-year deal as a free agent in March. San Francisco has made it clear he must continue to demonstrate positive behavior to remain in good standing with the team.

"The probability of a suspension was known when we signed Jerome," general manager Trent Baalke said in a statement. "Since joining the 49ers, Jerome has proven to be a great teammate. Although he will not be able to participate in the first six weeks of the season, Jerome has done everything asked of him, both on and off the field. We are in full support of the NFL's decision, and look forward to Jerome's future contributions to our organization."

Simpson can return to the active roster on Oct. 19, a day after the team's home game against the Baltimore Ravens. He can still participate in all preseason practices and games.

The 29-year-old wideout, who had been a candidate to be San Francisco's No. 3 receiver behind Anquan Boldin and Torrey Smith, served a three-game suspension to start last season with Minnesota before the Vikings cut him as he faced more trouble involving drugs and alcohol.

The suspension announced Tuesday stems from a legal case from summer 2014.

The 49ers have employed several players with legal problems in recent seasons, prompting CEO Jed York to say after 2014 ended that the team needed to be better. Excluding Simpson, San Francisco had 12 arrests involving seven different players since January 2012, most in the NFL.

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"Our mission is very simple: the San Francisco 49ers win with class. We haven't won, and I don't think we've conducted ourselves with the level of class that I expect of our organization," York said then. "We've had off-the-field issues. That's going to happen in sports. The level that it's happened here is not unacceptable."

Simpson was arrested in November 2013 on suspicion of drunken driving. Then in January 2014, he avoided jail time after pleading guilty to careless driving and refusing to take a DWI test. In return, prosecutors dropped a misdemeanor charge of driving while impaired. That case resulted in his 2014 suspension while with the Vikings.

Simpson also served a three-game ban in 2012, stemming from a felony drug conviction for a marijuana shipment authorities found at his home in Kentucky while he played for Cincinnati in 2011.

Simpson was still on probation for that '11 drug conviction in Kentucky at the time of the 2013 drunken driving arrest in Minnesota. As part of the plea deal for the 2013 incident, Simpson was placed on probation for a year.

A second-round pick by the Bengals in 2008, Simpson played his first four seasons in Cincinnati before joining Minnesota. His 726 yards receiving were a career high in 2013, which came on 48 receptions with one touchdown catch.