Over the last two seasons, San Diego’s defensive linemen could be sorted into one of two categories: “Corey Liuget” and “Hot Garbage.” This season, however, the D-line is on a steep and sudden upswing.

GM Tom Telesco signed free agent NT Brandon Mebane and used the No. 3 overall pick on DE Joey Bosa, giving the Chargers a trio of frontline starters on a unit that floundered for much of last season.

While the additions of Mebane and Bosa have the fans fired up, and rightfully so, the real reason for excitement on the defensive line is the admirable depth the Chargers have accumulated over the last few seasons.

Darius Philon, a 2015 sixth-round pick out of Arkansas, has a lot in common with Liuget; both are one-gap penetrators with the quickness and athleticism to thrive in San Diego’s hybrid scheme. Philon missed eight games as a rookie with a pectoral injury, but finished with five tackles and better pass-rush grade than Liuget (62.4 to 60.0), according to Pro Football Focus.

While Philon earned some impressive marks, fellow lineman Damion Square fared even better. The fourth-year player out of Alabama appeared in six games last season, including one start, and earned a pass-rushing grade of 70.0 (and an overall grade of 65.0). That was the highest mark of any Chargers lineman last season and was nearly identical to the grade Mebane earned (73.9) while playing in Seattle’s loaded defensive front seven.

It should be noted, in all fairness, that Philon and Square combined to play just 298 defensive snaps in 2015; Liuget played 444 defensive snaps by himself, despite missing five games. Nonetheless, Philon and Square showed enough that they have likely earned 20-25 snaps per game off the bench, with most of those coming in obvious passing situations.

As for stopping the run? The Chargers have a couple of young reserve linemen capable of that, too.

Perhaps no one benefitted more from the arrival of Mebane than backup NT Ryan Carrethers, who can now maximize his efficiency on a limited snap count. Carrethers has the size (6’1”, 337 lbs.), strength, toughness and durability to be a throwback 3-4 nose tackle. He struggled against the run last season, earning a 46.4 grade in that department, but he will tighten up his technique by learning from the savvy Mebane.

The Chargers will also welcome back Tenny Palepoi, who made the team as an undrafted free agent in 2014 but missed his sophomore season with a broken foot. The Utah product lacks Carrethers’ size and strength, but he has the quickness to run stunts and the hip snap to shoot gaps and disrupt plays in the backfield.

The average age of Philon, Square, Carrthers and Palepoi? Just under 25 years old.

This is not to mention veteran Sean Lissemore, who has started 13 of 26 games for the Chargers over the last two seasons. The way the youngsters have been playing, we won’t be mentioning Lissemore this fall, either.