After speculation that he'd go to New England, reportedly decided to sign a three-year contract with the San Diego Chargers.

Johnson is one of the many players exiting San Francisco this offseason.

Johnson will fill a void in San Diego left by Eddie Royal, who signed with the Bears last week. With Keenan Allen still in the fold, Johnson will be no more than the third option in the Chargers passing attack behind at least Allen and Antonio Gates.

He will need to gel with Philip Rivers quickly to surpass Malcom Floyd on the depth chart, too.

Johnson's Metrics

Depending on who you ask, Johnson may have been hesitant to return to the AFC East because his old buddy Darrelle Revis is back in New York. Regardless of the reason, it seems as though Johnson chose the better option given potential opportunity.

Last year with San Francisco, Johnson saw only 50 targets, by far the lowest he has seen over the past five seasons. Excluding his injury-plagued 2009 campaign, his 35 receptions last season was the lowest mark since his 2008 rookie season.

He added three touchdowns in San Francisco, but appeared to lack the spark that the 49ers were looking for in the passing game.

When you look at Johnson's metrics, however, you start to see that the surface numbers don't tell the entire story. For example, his Target Net Expected Points (NEP) total, which tells us the number of expected points Johnson added on all of his targets, was the highest of his career at 24.83. This probably has a lot do with the fact that he's played with bad quarterbacks in the past, but his Target NEP total was actually second best on the 49ers last year, behind only Anquan Boldin.

From an efficiency standpoint, Johnson's Reception NEP per target was also a career high 0.81, which was best on the 49ers last year.

Perhaps there's a little more left in the tank, after all...

I'm sure playing with Tom Brady was an enticing option for Johnson, but the guy in San Diego isn't too shabby himself.

Philip Rivers had another strong season in 2014, finishing eighth within our Passing NEP metric. Compared to Kaepernick, who finished 21st in the same metric (right behind Andy Dalton, for reference), Johnson is getting a significant upgrade at quarterback -- an upgrade he's never seen before.

When adjusted for strength of schedule, the Chargers finished ninth in the NFL last year in Passing NEP.

One of the biggest concerns with Johnson is his health, as he's missed seven games over the past two seasons. But given his metrics last year and the fact that he'll finally be playing with a strong quarterback, it's tough to not think positively about this move for Johnson. He certainly fills a void that the Chargers needed to fill.