First things first, Matt Tobin is not the answer to George Fant’s absence. The Seahawks traded a fifth-round pick in 2018 to the Philadelphia Eagles for Tobin and a seventh-round draft choice. Tobin is not, however, a left tackle.
Tobin has made 21 starts over the last four years. This includes starting 13 games in 2015. Of those 21 starts, 20 of them have been at guard. He did play left tackle and left guard in college at Iowa, however. Still, college was a long time ago.
Possibly, the Seahawks are thinking of Tobin in terms of being a backup at tackle and guard.