Question: Kelly Robert Pavlik, is an American former professional boxer who competed from 2000 to 2012, he won the unified WBC, WBO, "Ring" magazine and lineal middleweight titles, and made three successful defenses before losing them to Sergio Martínez, in which year, an Argentine former professional boxer who competed from 1997 to 2014?
Sentence (from "Sergio Martínez (boxer)"): Martínez's 50-month reign as lineal champion ranks as one of the longest in middleweight history.
Relevant evidence: No