It's been another frustrating season for the San Diego Chargers, and it got off to an inauspicious start in Week 1. Star wide receiver Keenan Allen was smoking the opposing Kansas City Chiefs play after play, building excitement in the fan base and along the sideline.

Then, suddenly, it all came to a halt.

Allen went down with a leg injury, and their worst fears were realized after the game: Keenan had torn his ACL.

Eventually, the Chargers blew a multi-touchdown lead to the Chiefs, a theme that, unfortunately for San Diego, proliferated the rest of the year. Late lead after late lead was blown.

After Week 5, the Chargers had a better point differential than the Raiders. They were 1-4, and Oakland was 4-1.

Luckily, the injury that served as a huge blow to the Chargers' air attack has been attacked back by Allen. His recovery is way ahead of schedule, illustrated by the workouts he's already going through.

From ESPN's Eric D. Williams:

San Diego Chargers WR Keenan Allen running sprints just four months after ACL knee surgery. Pretty impressive.

There's still plenty of work to be done, but this is a big step forward. If Allen keeps up this pace, he could return in time to participate in all of training camp.

In 2015, Keenan was on pace for 1,450 receiving yards through the first half of the season. His season was ultimately cut short after he suffered a lacerated kidney. If he can stay healthy, Allen has a chance to become one of the premier targets in the NFL.

At the young age of 24, that's a scary prospect for opposing defenses for years to come.