The 49ers haven't played their first preseason game and they've already lost one of their biggest 2017 free agent signings for the entire year. 

The team announced that Malcolm Smith suffered a torn pectoral muscle during practice on Saturday. Although the 49ers didn't specify how long Smith would be out, NFL.com has reported that the linebacker will miss the entire 2017 season. The freak injury happened while Smith was trying to tackle running back Matt Breida, according to ESPN.com

The loss means that the 49ers biggest defensive investment of the offseason won't be on the field at all this season. Smith was one of the few defensive free agents that the 49ers targeted in March, and they landed him after offering a five-year, $26.5 million deal that included $11.5 million in guaranteed money. 

Smith, 28, signed with the 49ers after spending two years in Oakland. He started his career with the Seahawks in 2011 and was MVP of Super Bowl XLVIII. Smith signed with the Raiders in 2015. 

The injury to Smith means the 49ers will likely have to put rookie Reuben Foster on the field a little bit earlier than planned. 

According to 49ers defensive coordinator Robert Saleh, the original plan was to work Foster into the lineup slowly. 

"The best way I can explain with Reuben is he'll get his opportunity when he absolutely, absolutely deserves it," Saleh said before Smith's injury. 

With Smith now out, there's a good chance Foster will be joining Ahmad Brooks and NaVorro Bowman as one of the team's starting linebackers. The 49ers clearly like Foster, otherwise they wouldn't have traded up to grab him during the first-round of the NFL Draft.  

Back in April, the 49ers traded up from the second round to grab Foster with the 31st overall pick.