The eyeball test of Mike Zimmer's first season with the Vikings suggested that the neophyte head coach was a little bit on the conservative side. As it turns out, the numbers support that.

Our friends at Football Outsiders have released their annual "Aggressiveness Index" to rank how aggressive coaches were in certain game-management situations. Zimmer ranked 20th out of 32.

How is it calculated? It looks at how likely coaches were to go for it in fourth-down situations, excluding "obvious catch-up situations" like trailing late when teams have no choice but to go for it.

According to their charting, Zimmer went for it on seven in the team's 102 applicable situations. More specifically, he went for it on 4-and-1 in four of 13 situations and 4th-and-2 in two of nine.

The gutsiest fourth-down call Zimmer green-lighted was a tricky fake punt play against the Bears in Week 11. On that play, safety Andrew Sendejo caught a direct snap and ran around left end for 48 yards and a first down. That successful fake set up a Teddy Bridgewater touchdown pass.

The Aggressiveness Index also looked at situations when a drive stalled somewhere between an opponent's 31- and 37-yard lines. In eight such situations last season, Zimmer didn't go for it once.

Zimmer was the least aggressive coach in the NFC North in 2014, according to Football Outsiders. Marc Trestman, formerly of the Bears, trailed only Saints coach Sean Payton in the aggressiveness rankings. Jim Caldwell of the Lions was third. And Mike McCarthy of the Packers ranked 10th.

Perhaps the fact that Zimmer had a young team, including a young quarterback, led to him being a little cautious on fourth down. We will see if Zimmer gambles more this upcoming season.