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.