Once Caldas had finished, he returned to Colo-Colo in June 2008, despite Fernando Astengo not planning on featuring him in the team,. Millar made his first start against Universidad de Chile in a Copa Gato match that ended in a 2–1 victory at Tierra de Campeones Stadium in Iquique. Despite several starts, he found it difficult to break into the first team, with Astengo preferring to use him as a substitute.. With the arrival of Marcelo Barticciotto as coach, he was given a more permanent position in the first team, providing consistently good performances as a result. On 8 November 2008, Millar scored his first goal in the Barticciotto era against Cobresal in a 1–1 home draw. In the Championship playoffs second leg final, Millar was proclaimed a champion for third time in his career, after he scored the goal of the championship in the 3–1 victory against Palestino, by eluding the goalkeeper Felipe Núñez and playing masterfully. On 14 February 2009, Millar scored his first goal of the season in an Apertura tournament match that ended in a 2–0 victory over Universidad de Concepción at Estadio Monumental, where he scored the first goal of the game. On 22 April, he scored a goal in a Copa Libertadores match that ended in a 2–1 loss against Sport Recife in Brazil. He also scored the first goal at Colo-Colo's 5–2 win over Cobresal. At the end of season, Millar become the first footballer to contract swine flu on 16 June. He made a full recovery for the start of the Torneo Clausura. During the 2010 season he performed consistently well with Colo-Colo, and was selected for Chile's FIFA World Cup 2010 team and voted the Chilean Footballer of the Year in the Anfp awards. His club lost the championship, finishing three points behindUniversidad Católica. Millar was approached by Toluca who were impressed by his consistently good performances. However he never moved to Mexico and remained in Chile. In the 2011 season Millar was promoted to captain, due to the departure of Arturo Sanhueza to Deportes Iquique, but was stripped of the captaincy because of the departure of coach Diego Cagna and the arrival of Américo Gallego. Atlas In 2013, he was signed by Club Atlas, he debuted with Atlas in the 0–1 away defeat vs Tigres UANL. He scored his first goal in a 2–1 home victory over Club América. Prior