By late November, manager Rafael Benítez gave Lucas his chance to start a game in the Liverpool midfield after easing him in during his first few months at the club. Lucas scored his first goal for Liverpool on 27 January 2008 when he curled a 25-yard shot into the top corner during an FA Cup match against Havant & Waterlooville, becoming the first-ever Brazilian to score for Liverpool.
Lucas returned with a bronze medal and Benítez had high hopes for the Brazilian's future, stating, "This season he will improve because he is a very, very good professional and has experience of the Olympic Games." Lucas noted that Liverpool's squad was much improved from the previous season and relished the opportunity to compete for trophies, despite the increased difficulty of getting a first-team place. However, after a number of disappointing performances, both critics and fans voiced concerns about Lucas' quality and his confidence was further knocked when Liverpool fans booed him after a lacklustre draw against Fulham. The criticism irked Benítez and he responded with a passionate defence of the player, saying that "people just don't know how good Lucas is." Benítez also underlined Lucas' credentials, stating that he had been captain for both Grêmio and his national youth team, and that competing for place against Javier Mascherano, Steven Gerrard and Xabi Alonso was inherently difficult. Lucas' performances in December 2008 for Liverpool drew him much praise from pundits, the highlight being his performance in the 5–1 thrashing of Newcastle United, where he provided an assist for Gerrard. Lucas was sent off in a cup tie against Mersey rivals Everton, which Liverpool lost. This compounded his growing unpopularity amongst Liverpool's supporters, after he gave away a late penalty in Liverpool's previous match, a 1–1 draw with Wigan Athletic.
On 19 August, Lucas was shown a red card in the 2008 Olympics semi-final match between Brazil and Argentina, after a challenge on then Liverpool teammate Javier Mascherano, as Argentina ran out 3–0 winners. In August 2009, Lucas was recalled to the senior Brazil squad in place of Flamengo's Kléberson, who was absent through injury. After missing out on the Brazil world cup squad in South Africa, Lucas played the full 90 minutes in a friendly against the United States on 10 August 2010.