Chris Humphreys-USA TODAY Sports

The already low expectations for the San Francisco 49ers have fallen further after the NFL suspended linebacker Aaron Lynch for the first four games of this season.

Per the 49ers' official website on July 15, Lynch was suspended for violating the NFL's substance abuse policy.

San Francisco general manager Trent Baalke issued a statement in the official release about Lynch's suspension: “While disappointed to hear the news regarding Aaron today, we support and respect the league’s decision. We are confident that he will learn from this matter and that he understands what is expected of him moving forward.”

On Sunday, Lynch spoke about the suspension. As Matt Maiocco of CSN Bay Area writes, Lynch's "failed test this offseason was a result of drinking too much water."

“It came out unreadable,” Lynch said, per Maiocco. “I’ve already been in the program, so that’s (suspension) the next step.”

The 49ers drafted Lynch out of South Florida in the fifth round of the 2014 draft. Analysts believed his talent was much better than his draft position, but NFL.com's Nolan Nawrocki called him a "classic underachiever" with a "questionable effort, motor and desire."

In two years with the 49ers, Lynch has developed into a dependable pass-rusher. He has recorded 12.5 sacks in 30 career games, tying for the team lead with 6.5 sacks last season.

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According to Jeff Deeney of Pro Football Focus, Lynch ranked fifth among 3-4 outside linebackers in pass-rush efficiency last year behind Pernell McPhee, Justin Houston, DeMarcus Ware and Von Miller.

The loss of Lynch for four games is a crushing blow to a San Francisco defense that is still trying to rebuild its talent pool. The 23-year-old is a standout and seemed poised to take another step forward in his development.

Without Lynch, the 49ers still have Ahmad Brooks, who also had 6.5 sacks last season, to get after the quarterback. Two more important pieces who need to step up are their most recent first-round draft picks: Arik Armstead and DeForest Buckner.

Armstead showed great promise as a rookie, with Deeney noting he had 38 quarterback pressures in 250 pass-rush snaps. Buckner is a tremendous athlete who went seventh overall in April's draft.

If the 49ers are going to move forward in 2016 with Lynch out for 25 percent of the season, Armstead and Buckner have to become forces on the defensive line.