Per Levi Damien of Silver & Black Pride, Alexander's suspension will be for four games.
In a statement from an NFL spokesperson, via ESPN's Paul Gutierrez, Alexander will be eligible to return after the Raiders' Sept. 30 game against the Cleveland Browns:
A seventh-round draft pick out of LSU in 2016, Alexander emerged as part of Oakland's offensive line rotation as a rookie. The 24-year-old has appeared in 24 games, including nine starts, over the past two seasons.
Donald Penn is entrenched as Oakland's starter at left tackle. The team selected offensive tackle Kolton Miller with the 15th overall pick in the 2018 NFL draft, and he could be in line to start right away with Alexander out of action for the first four games of the season.