2009-10: In his seventh year in Switzerland's A league, Raphael Diaz had a career-high 31 points as a 23-year-old and also skated for Switzerland in the 2010 Olympic Games in Vancouver. he scored 4 goals with 27 assists in 49 regular season games for Zug. Zug reached the playoff semifinals after finishing third in the 12-team league. Diaz scored 1 goal with 5 assists and had 10 penalty minutes in 13 playoff games. In five games at the Olympics with eighth-place Switzerland he was minus-two with no points and 4 penalty minutes.
2010-11: Diaz was the leading scorer amongst defensemen for Zug, scoring 12 goals with 27 assists in 45 games and finishing plus-14 with 26 penalty minutes. Zug finished fourth in the A League and again reached the playoff semifinals. Diaz scored 2 goals with 4 assists and was minus-nine with 4 penalty minutes in 10 playoff games. After playing alongside former Montreal Canadians Glen Metropolit and Paul DiPietro with Zug, Diaz signed a one-year entry-level contract with Montreal in May 2011.
2011-12: Diaz made the Canadians after an impressive training camp and skated in 59 games for Montreal in his rookie season – missing 16 games at the end of the year due to a groin injury. Diaz scored 3 goals with 13 assists and was minus-seven with 30 penalty minutes, averaging 18 minutes of ice time per game. He was re-signed as a restricted free agent to a two-year contract by the Canadians in July, 2012.
Diaz was dealt by the Montreal Canadiens to the Vancouver Canucks in exchange for Dale Wiese in February of 2014. Diaz was dealt again, from the Canucks to the New York Rangers, at the 2014 NHL Trade Deadline.