Sunderland were relegated again in the 2005–06 season. At the end of the season, Arca went on to make twenty–six appearances and scoring two times in all competitions. It was announced that Arca would leave Sunderland, with the decision first being made in April 2006. He stated that he would not play in the Championship again should the club be relegated. By the time he departed Sunderland, he made 177 appearances and scoring 23 times for the side in all competitions. Five years later, Arca was named Solid Gold XI on the club's website. Middlesbrough On 26 July 2006, it was announced that Arca had signed a five-year contract with Premier League side Middlesbrough, for a reported transfer fee of £1.75 million, becoming new manager Gareth Southgate's first ever senior signing; they beat Spanish club Espanyol to signing the player. He was a replacement for Franck Queudrue, who moved to Fulham. Arca made his Premier League debut for Middlesbrough against Reading on the opening day of the 2006–07 season; he broke his foot and was substituted at half-time for Andrew Davies. After regaining fitness, Arca made his return to the first team, coming on as a late substitute, in a 1–0 win over Everton on 14 October 2006. With the progress of Andrew Taylor at left-back, Arca had been utilised as central midfielder. He scored his first goal for the club against Charlton Athletic on 23 December 2006. Arca then scored against Charlton Athletic for the second time this season, in a 3–1 win. His third goal of the season came on 17 February 2007, in a 2–2 draw against West Bromwich Albion in the fifth round of the FA Cup; leading to a FA Cup, which they won on penalties and Arca was one of the players successfully convert. He set up an equaliser goal for Lee Cattermole, in a 2–2 draw against Manchester United in the sixth round of the FA Cup; leading to a FA Cup replay once again, which Middlesbrough lost 1–0. However, Arca suffered a groin injury that saw him sidelined for a month. It wasn't until on 28 April 2007 when he returned from injury, coming on as a substitute during the second half, in a 3–2 loss against Tottenham Hotspur. Arca later featured the remaining two matches of the season. At the end of the 2006–07 season, he went on to make twenty–eight