[5] After recovering from a serious knee injury, Hines was given number thirty-eight shirt for the 2006–07 season[6] and on 16 January 2007, he scored on his first team debut with a scorching effort from outside the box against Hull City in the FA Cup Third Round.

[7] After making another appearance against Bristol City in the fourth round of FA Cup, which saw them through in the penalty shoot-out,[8] Hines, however, suffered an injury that kept him out for the rest of the season.

[17][18][19] Having impressed from limited opportunities during the 2010 season, on 11 December 2010, Hines replaced the suspended David Wheater alongside Matthew Bates in the starting line up of Middlesbrough's defence for the club's 1–0 victory over Cardiff, where he was rewarded with the Man of the Match award.

[20] Seb continued to impress with assured performances at the heart of the Middlesbrough's defence with a cool display in the draw at Preston North End and another commanding showing in the 2–0 victory over Scunthorpe United on 1 February 2011 in which the highlight was a fine measured lob by prolific goalscorer Kris Boyd which brought about his 200th career goal.

[39] After making one appearance in the 2008–09 season for the club, which came against Hull City on 6 December 2008,[40] it was announced on 5 January 2009, Hines signed on loan for one month at Derby County.

[45] Two days later, on 14 February 2009, Hines made his Oldham Athletic debut, making his first start, in a 2–1 win over Northampton Town.

[47] After appearing three times at the start of the season at Middlesbrough, Hines joined League One side Coventry City on loan until 4 January 2014.

[49] Since making his debut, Hines became a first team regular at the club throughout September and October until he suffered a hamstring injury that kept him sidelined for six weeks.

[59] It wasn't until on 25 September 2015 when he made his first start before coming off in the 34th minute after suffering an injury, in a 5–2 win over New York Red Bulls.

[65] After appearing absence on two occasions in two weeks between 15 May 2016 and 26 May 2016,[66][67] Hines scored his second goal of the season, in a 2–2 draw against San Jose Earthquakes on 18 June 2016.

[74] Hines is also eligible to play for the United States national team, as his father is an American citizen who served in the US military.

[75] Hines has been called up for the England U19 squad for the first time in late-September 2006[76] and made his debut against Spain on 7 October 2006 in Austria to prepare for the European Under-19 Championship Tournament.

[79] On 7 June 2022, Hines was promoted to Orlando Pride interim head coach when Amanda Cromwell was placed on administrative leave.

[81] On 11 November 2022, Hines signed a multi-year contract to become head coach of the Pride, removing the interim tag.

[84] On 23 November, Hines coached the Orlando Pride to the club's first NWSL championship, completing the domestic double.