On 30 September 2014, Martínez came on as a substitute in a Champions League group stage match away to Shakhtar Donetsk, with his team trailing 2–0 to the Ukrainian hosts. In the 89th minute, he scored a penalty and then equalised in added time for the final score of 2–2 to complete a comeback which was dubbed "stunning" and "remarkable" by UEFA. Martinez was voted Player of the Month for December 2014 and January 2015. In the Champions League quarter-final first leg on 15 April 2015 against Bayern Munich, he scored the last goal in a 3–1 victory and also won the penalty that Ricardo Quaresma scored for the opening goal after being fouled by goalkeeper Manuel Neuer. Martínez netted again in the second leg six days later, heading a consolation from Héctor Herrera's cross as Porto lost 1–6 at the Allianz Arena, thus being eliminated from the competition.