After starting out at Miramar Misiones he went on to play for a host of teams in several countries, mainly Porto and Inter Milan, winning eight major titles with the former club while appearing in 118 competitive matches (three goals).

[3] In Pereira's second season at the Estádio do Dragão, he featured in 21 Primeira Liga games (all starts), adding 12 UEFA Europa League appearances as Porto won the treble.

He also started in that campaign's Portuguese Cup final against Vitória de Guimarães on 22 May 2011, scoring an own goal in the 21st minute to bring the sides level in an eventual 6–2 victory.

[4] After Porto rejected an offer from Premier League side Chelsea in the summer for Pereira, he signed a new contract on 3 October 2011 running until 2016, with his release clause remaining at £25.7 million.

[5] In late December, he heavily criticised Manchester United's Patrice Evra for reporting alleged racist abuse from Pereira's national team colleague Luis Suárez – including a claim from Evra that Suárez "doesn't speak to black players" – saying that "what happens on the pitch stays on the pitch", adding that the Frenchman would have to "wear body armour" if the players' future international friendly was to take place immediately instead of in late 2012.

[27] Having played only eight competitive games during his tenure, Pereira became a free agent and returned to Paraguay, signing for Club River Plate (Asunción) in January 2020.

[33] Pereira was selected to the 2011 Copa América in Argentina, being first-choice and scoring two goals in the group stage, including the game's only against Mexico[34] as Uruguay won its 15th continental tournament.

[36] On 19 June, in the second group game against England, he was struck unconscious after being kneed in the head by Raheem Sterling, but refused to be replaced after recovering[37] and went on to feature the full 90 minutes in the 2–1 win.