Usually, when a new head coach comes to an NFL franchise, he cleans house on the coaching staff. For the San Francisco 49ers, Chip Kelly may not be so quick to dismiss the assistants amassed under one-hit wonder Jim Tomsula. According to a Monday morning report from Alex Marvez of Fox Sports, there's a "strong possibility" that defensive coordinator Eric Mangini will remain in place going forward.

Source tells @NFLonFOX there's "strong possibility" Eric Mangini returns as @49ers defensive coordinator. Makes sense w/his 3-4 background

— Alex Marvez (@alexmarvez) January 18, 2016

It seems a smart move on Kelly's part. Mangini is well versed in a base two-gap, 3-4 defense. Kelly, going back to his Oregon days, has always preferred such an alignment because of the increased athleticism on the field on defense and special teams in the form of linebackers. Outside linebackers in the 3-4 tend to be smaller and more athletic than their counterparts in the 4-3, defensive ends.

The 3-4 is also the perfect defence to stop Kelly's own power-spread, read-option offense as the three down linemen stack, read and shed and the four linebackers behind them work to the ball.

Keeping a coordinator who has a track record of success despite a difficult year in San Francisco following a mass exodus of defensive talent, especially one who runs your preferred system and can help with a sense of continuity during a time of extreme change, makes sense.

Whether Mangini (or anyone) can find a way to field a successful unit playing opposite Kelly's breakneck offense though, is another question entirely.