San Diego linebacker Donald Butler has developed into one of the Chargers' best defensive players, and the Chargers will likely attempt to keep it that way.

More: Bolts From The Blue

Butler is entering the final year of his rookie contract, and San Diego is expected to approach Butler about a long-term extension soon, according to U-T San Diego. After missing his rookie season due to an Achilles injury, Butler has played a significant role for the Chargers the last two seasons. With veterans like Takeo Spikes and Shaun Phillips departing this offseason, Butler is not only one of San Diego's top defenders, he's also one of the defensive leaders.

Despite missing his first season, the former third-round pick stepped into a starting role immediately upon his return. He started 16 games in 2011, racking up a career-high 96 tackles. Butler maintained a similar level of production last season, despite missing four games due to a groin injury. He started 12 games, finishing with 77 total tackles, three sacks, four pass deflections and an interception.

Productive players entering the prime of their careers don't often hit the free agent market, so it shouldn't be a surprise if San Diego attempts to lock up Butler. At 24, Butler is just entering his best years, and as a result could be in line for a lucrative long-term deal. Dannell Ellerbe signed a five-year, $34.75 million deal with the Miami Dolphins this offseason. Ellerbe is two years older than Butler, has a longer injury history and less of a track record of production.

If the two sides don't come to terms on an extension this offseason, Butler could command a contract worth upward of $7 million per season if he turns in another strong season in 2013.

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