NFL: Chicago Bears at Arizona Cardinals
Mark Sanchez is suspended for four games. USATSI

Former first-round pick Mark Sanchez, who has found a second life in the NFL as a quarterback mentor, hasn't taken the field in a regular-season game since the 2016 season. At this point, it's unknown if he'll ever get another chance to play meaningful football again, but what we do know is that his wait will continue for at least four more games.

That's because on Friday the NFL suspended Sanchez four games for violating the league's performance-enhancing drugs policy. As NFL Network's James Palmer noted, he'll still be eligible to participate in offseason activities including preseason practices and games -- if he gets signed, of course.

In a lengthy statement posted on Instagram, Sanchez blamed the infraction on an "accidental exposure" to a banned substance.

The NFL has informed me that I have tested positive for a substance on the banned substance list. I was blind-sided by the news and I want to say unequivocally that I have never cheated or attempted to gain a competitive advantage by using a banned performance enhancing substance. During the past 9 years as an NFL player I have been subject to 73 drugs tests — an average of over 8 tests per season — and all but one have been clean. I have taken the same regimen of supplements for the past five years without any issues. The timing and results of my tests establish circumstances of unknowing supplement contamination, not the use of performance enhancing substances.

My test history and pharmacological science confirm I was not cheating and the positive test was the result of incidental and isolated exposure to a banned substance. I was tested by the NFL 30 days before and 12 days after my one positive test. Both tests bracketing the one positive test were clean. Experts in the field have advised me that an athlete seeking to gain the benefit of the performance enhancing substance would take the substance in large quantities, over several weeks. Therefore, one or both of the bookend tests would have resulted in a positive test. Furthermore, the trace amount of the substance found in the one positive test is consistent with a one-time and accidental exposure. 

Nevertheless, the NFL has an extremely comprehensive performance enhancing drug policy. Because of the policy's comprehensive and self-described "strict liability" nature, players know the inadvertent exposure to a banned substance may lead to a positive test. The policy makes it each player's responsibility to avoid even the unwitting ingestion of a banned substance. I accept responsibility as a professional and will move forward with greater caution in the future. I look forward to getting back onto the field this season.

Sanchez, taken fifth-overall by the Jets in the 2009 draft, started four seasons in New York before landing in Philadelphia, where he started 10 games over the course of two seasons with the Eagles. At this point, Sanchez's career has been reduced to quarterback mentor and third-string quarterback. He mentored Cowboys quarterback Dak Prescott during his rookie season, when he was suddenly thrust into the starting role in the aftermath of Tony Romo's back injury. And he helped mentor Bears quarterback Mitchell Trubisky during his rookie season in 2017.

While no NFL team was likely to offer him a job to actually play football, this might still impact his ability to get signed as a backup, though as previously noted, he can still participate in preseason games. If this is the end of his career, he'll fittingly finish with 86 touchdowns and 86 interceptions.