2017 was a crazy year for the UFC Middleweight division. The division crowned two new champions (under the weirdest of circumstances) and saw longtime veterans of the sport slowly move down in the rankings.
At the end of the year, the fighter with the biggest improvement in the division was Robert Whittaker. Whittaker started the year as the number six-ranked Middleweight in the world. By the end of the year, Whittaker had moved up six spots to the championship position. He did this by defeating Middlweight standouts Jacare Souza and Yoel Romero.
Georges St-Pierre had an equally impressive year, making his Middleweight rankings debut in the championship position after defeating Michael Bisping at UFC 217. After vacating the championship, GSP dropped to #4.
Bisping fell the furthest out of any Middleweight, losing his championship and a fight to Kelvin Gastelum all in the same month. Bisping started 2017 as champion and dropped to #7 by the end of the year.
The Strikeforce Middleweight trio had a mixed year of results, but ended up staying put in their ranking (Yoel Romero #1, Luke Rockhold #2, Jacare Souza #3).
Kelvin Gastelum made a big push in 2017, defeating Vitor Belfort and Bisping to move from #10 to #6. David Branch made his return to the UFC in 2017, finishing the year at #10 with a win over Krzysztof Jotko and a loss to Luke Rockhold.