For the Clausura 2010, on 13 February 2010, James scored a golazo in the match against archrivals Lanús with a left-footed lob to make the game 2–0 in the final minutes. After the game, daily sports website Diario Olé compared his playing and personal style to Cristiano Ronaldo and nicknamed him the "James Bond of Banfield".
On 10 February 2010, James scored his first Copa Libertadores goal in a 2–1 home victory over Mexican club Monarcas Morelia. James added to his glowing reputation a week later with a goal in a daunting victory over Copa Libertadores group rivals Deportivo Cuenca away from home, scoring the fourth goal of the game with a nice finish in the area on his left foot. Banfield thrashed the home team 4–1. His wonderful scoring season continued with a brace in the Copa Libertadores group game on 10 March 2010. In an away match against Uruguayan club Nacional, James scored first with a diving header and then from the penalty spot on his right foot. The game ended with a 2–2 draw. The 18-year-old netted another goal against Brazilian club Internacional on 29 April 2010 in the first leg match of Copa Libertadores 2010 Round 16, which Banfield won 3–1. This goal brought his tally to five goals in seven games. However, James' international season ended in defeat as his team went down on away goals with a 0–2 defeat in Porto Alegre in the second leg, in which James was red carded for two fouls.
On 6 July 2010, James was signed by Porto for €5.1 million, with 30% economic rights retained by other parties. He signed a four-year contract with a €30 million release clause. Porto later re-sold 10% economic rights to third parties. On 18 July, he played his first game and scored his first goal in a friendly against Ajax. In November, Porto sold 35% economic rights (half of 70%) to Gol Football Luxembourg, S.A.R.L. for €2.5 million.
On 15 December 2010, James scored his first competition goal in Europe in a 3–1 home victory against Bulgarian club CSKA Sofia. James scored a hat-trick and assisted once against Vitória de Guimarães in the 2011 Taça de Portugal Final, which Porto won 6–2. On 17 May, Porto bought the remaining 30% economic rights from Convergence Capital Partners B.V. for €2.25 million and once again hold more than half of the economic rights with 55%. On 13 June, James signed a new five-year contract in which the release clause increased to €45 million. In no more than 24 appearances did he score six goals, provide eight assists and play a part in the Europa League victory. He finished the 2010–11 season with six goals in 31 appearances.