Roster analysis: Stevie Johnson the X-factor for Chargers' receivers

SAN DIEGO -- After an uneven performance in a one-year stint with the San Francisco 49ers, receiver Stevie Johnson appears to have found a home with the San Diego Chargers. The 28-year-old signed a three-year, $10.5 million contract with the Chargers in free agency and has developed a good rapport with quarterback Philip Rivers during offseason work.

Lock: Malcom Floyd, Keenan Allen, Jacoby Jones, Johnson

Looking good: Dontrelle Inman

On the bubble: Austin Pettis, Javontee Herndon, Torrence Allen, Titus Davis, Tyrell Williams, Demetrius Wilson.

The good: San Diego’s top six targets on the depth chart are 6-foot-2 or taller, so Rivers will have several big receivers on the perimeter at his disposal. Heading into his 12th year, Floyd likely will make 2015 his final season in the NFL. Still, the 33-year-old receiver remains San Diego’s most effective deep threat. Keenan Allen and Johnson are both similar in stature and route-running ability, so they can be used in a similar manner by offensive coordinator Frank Reich. Jones gives San Diego another receiver who can stretch the defense vertically. Inman has built on his impressive performance during the final two games of 2014 and could work his way into the receiver rotation if he can find a job on special teams. Pettis, Herndon, Torrence Allen and Davis all flashed at times during offseason work and will compete for jobs on the back end of the roster.

The bad: The only thing San Diego lacks is a true burner on the perimeter who can take the top off of a defense. Keenan Allen said he’s losing weight in order to play faster once the regular season begins. While the Cal product still had decent production in his second year in the NFL, he struggled shaking loose against the top corners in the league. Replacing the production Eddie Royal provided will be tough in 2015. However, the Chargers will use a combination of Johnson, tight end Ladarius Green and running back Danny Woodhead to work the middle of the field.

Bottom line: The wide receiver group should be a plus for San Diego’s offense, and it should compete for the best combination of players at that position in the AFC West. Floyd provides familiarity and stability as the elder statesmen of the group, while Keenan Allen should be more productive in Year 3. But the X-factor will be Johnson and the impact plays he can produce in critical situations for this offense. “It’s a challenge,” Johnson said. “And I think every competitor likes a challenge. That’s what I’ve been thrown into, learning a whole new playbook and then going at the speed that the Chargers are going at. It’s a challenge, but I feel like once we get it, we should be unstoppable.”