 Complete the following phrase:  Mascherano made his debut for Liverpool against Sheffield United on 24 February 2007, and was praised by the Liverpool manager Rafael Benítez and team captain Steven Gerrard after Liverpools 40 victory. After playing in a match against Arsenal on 31 March, Benítez called Mascherano a monster of a player. Similarly, his teammates were impressed by his talent; Xabi Alonso noted how mature a player he was for his age, saying, He has a cool mind on the pitch. He is analysing and thinking about the game in each moment. Mascheranos first Champions League appearance came in the quarter-final first leg away to PSV Eindhoven on 3 April. Hastily establishing himself as a starter at the club, Mascherano played in the 