brent grimesThe San Diego Chargers are fresh off a run that saw them bow out of the playoffs in the Divisional Round. Although a talented team, the Chargers are also a team that has a lot of holes on their roster.

The team can only do so much to improve through the Draft, so some holes are going to need to be plugged via free agency.

Here are five free agents that San Diego absolutely has to make a run at in order to improve their team.

1. Brent Grimes, Cornerback

The cornerback position was beyond awful for the Chargers in 2013. The team is expected to pick a cornerback in the first round of the upcoming draft, but that's not nearly enough.

If San Diego can secure one of the many top cornerbacks hitting the market, they can turn a weakness into a strength in due time. The main reason I put Grimes here over the other top-line corners, like Alterraun Verner and Vontae Davis, is that Grimes has the lowest likelihood of being franchised (in the case of Davis) and would likely come cheaper than Verner considering he's still only a year off of a serious achilles injury.

2. Walter Thurmond III, Cornerback

Even with the team likely to draft a corner, the team could absolutely be best served by double-dipping into the free agent pool at the cornerback position. Thurmond has had a ton of character issues, but he was also one of the league's best No. 2 cornerbacks for Seattle before that all happened. The Chargers can afford to gamble on Thurmond here, as he'll likely come cheap and would help the team improve greatly in the back end.

3. Louis Delmas, Safety

Yeah, the Chargers' secondary is really bad. Alongside the great Eric Weddle, safety Marcus Gilchrist was regularly burned in deep coverage, and improving the safety position will help the team mask some of its deficiencies at cornerback. Considering the small amount of cap space San Diego currently has, I expect the team to go after Delmas rather than a higher-profile safety, at a cheaper price.

4. Daryl Smith, Linebacker

Donald Butler is a pending free agent, but he wasn't very good anyway. The Chargers, with all their problems at the back end, cannot allow their front seven to lag behind, so signing a great inside linebacker like Smith is a must. After being underrated for years, the veteran linebacker finally received some attention for his play because he left Jacksonville for Baltimore, and provided solid run defense. This is an important move that the Chargers have to make to be successful in 2014.

5. Geoff Schwartz, Guard

Jeromey Clary's as good as gone. The guard is one of the most expensive players on San Diego's roster and played like crap this past season. While the team hopes to retain guard Chad Rinehart on the other side, the team should also make a run for guard Geoff Schwartz, who has bounced around different teams in the past couple of years and performed well for every single one of them. Given Schwartz's underrated status, he could come cheap for the team as well, so he is definitely a player worth targetting for the Chargers.