Early career Born in
Wellington, Killen grew up in the Wellington suburb of
Island Bay. As a youth he attended
Rongotai College. He represented the college in junior grades and was selected to tour Australia with the New Zealand Secondary Schools representative team in 1998, along with future "
All Whites"
Leo Bertos and
Tony Lochhead. Killen played his club football for
Miramar Rangers, whose
coach arranged a trial with
Manchester City. The trial was successful. The 17-year-old Killen joined City's
youth academy. His first senior club appearances came during a
loan spell at
Second Division side
Wrexham in September 2000, then managed by
Brian Flynn. He scored his first league goal on 9 September against
Oldham Athletic, and in total scored three goals in nine appearances for the Welsh club. The following season, he was loaned to
Brian Horton's Second Division
Port Vale. He scored on his debut on 25 September, in a 3–1 win over former club Wrexham at the
Racecourse Ground. He made two further substitute appearances that season, and finished as top goalscorer for the
reserves.
Oldham Athletic He joined
Oldham Athletic in July 2002, after manager
Iain Dowie spent
£250,000 to acquire the young striker. He scored just four goals in 33 appearances in
2002–03. During the
2003–04 campaign, he featured 13 times, scoring two goals. Killen was the
club's top scorer in the
2004–05 season, with 15 goals in 30 starts. After Killen had left the club, recently appointed manager
Ronnie Moore claimed that Killen had "underachieved" during his time with the club.
Hibernian In January 2006, Killen joined
Hibernian (Hibs) on a free transfer. He made his debut against
Hearts on 28 January, and then scored on his second appearance as he netted the third goal in Hibs' 3–0 defeat of
Rangers at
Ibrox in the
Scottish Cup fourth round on 4 February. Four days later he scored his first goal at
Easter Road, the opener in a 7–0 win over
Livingston. He scored five goals for Hibs by the end of the
2005–06 season. Killen scored the opening goal in a 5–0 win over Latvian club
Dinaburg in the
UEFA Intertoto Cup second-round game at Easter Road on 2 July 2006. Following the departure of strikers
Garry O'Connor and
Derek Riordan, Killen was expected to be an important player for Hibs in the
2006–07 season. By December 2006, he had scored 11 goals, including two in a 2–1 win over Rangers. During a 2–2
Scottish Cup draw with
Aberdeen in January, however, Killen suffered a ruptured
Achilles tendon which ended his season. Killen's contract with Hibernian expired in the summer of 2007 and he rejected the offer of a one-year extension from the
Edinburgh club.
Celtic Killen was expected to sign for
Cardiff City, but he instead signed for
Celtic on a three-year contract in May 2007. Killen made his debut on 5 August, coming off the bench in a goalless draw against
Kilmarnock at
Celtic Park. His first goal for the club came on 7 October at
Fir Park; with Celtic trailing 1–0 to
Gretna, Killen equalised in the 89th minute before
Scott McDonald scored the winner for Celtic in stoppage time. He made his
UEFA Champions League debut on 3 October in a shock 2–1 victory over
AC Milan at Celtic Park. He made just three league starts in
2007–08, though came off the bench 24 times. After that, however, he found chances hard to come by as he found himself behind Scott McDonald,
Georgios Samaras and
Jan Vennegoor of Hesselink in the pecking order. Killen played mostly for the Celtic reserve team and hardly featured in the first team. On 31 January 2009, Killen joined
Championship side
Norwich City on loan for the remainder of the
2008–09 season. He made his first appearance for
Bryan Gunn's "Canaries" in a 3–3 draw to
Wolverhampton Wanderers at
Molineux on 3 February, before he returned to training with Celtic after only making four substitute appearances at
Carrow Road. At the end of the
2008–09 season, manager
Gordon Strachan resigned and was replaced by
Tony Mowbray, who had previously managed Killen at
Hibernian. Killen's hopes of regaining a first-team place at Celtic for the
2009–10 season were boosted in pre-season
friendly matches, as he scored two goals against
Brisbane Roar and came off the bench to score in a 5–0 win against
Al-Ahly. Killen then started Celtic's following pre-season match against
Tottenham Hotspur, and he opened the scoring in this match with a neat
headed finish following a pinpoint
cross by teammate
Paul Caddis. A further goal against
Manchester City ensured he finished pre-season with five goals in five games. He scored his first league goal at
Celtic Park on 20 September, Celtic's first goal in a 2–1 win against
Hearts. Three days later he scored against
Falkirk at
Falkirk Stadium in a 4–0 win in the
League Cup.
Middlesbrough Killen returned to England in January 2010 and joined his former Celtic manager
Gordon Strachan at
Middlesbrough, along with teammates
Willo Flood and
Barry Robson. He scored his first goal at the
Riverside Stadium on 9 February, in a 2–1 win over
Barnsley. He scored two further headed goals in Championship games against
Reading and
Preston North End, but left the club after the end of
the season when his contract expired in June 2010.
China After being released by Middlesbrough, Killen signed a year and half contract with
Chinese Super League side
Shenzhen Ruby in July 2010, then managed by
Siniša Gogić. Killen scored his first goal for the "Youth Army" on his debut against
Liaoning Whowin at the
Tiexi New District Sports Center on 28 July 2010. He finished his first half-year at
Shenzhen Stadium with eight goals from 13 matches to help the club to avoid
relegation by a two-point margin. The club were relegated in
2011 after finishing bottom of the league under
Philippe Troussier, despite Killen's nine goals. Killen signed a contract with
China League One club
Chongqing on 17 February 2012; the club play at the 58,680 capacity
Chongqing Olympic Sports Center. He finished the
2012 season as division's fourth highest scorer on 17 goals from 26 starts. ==International career==