Shaughnessy started his career at English club Reading, joining in 2012 after a successful trial and signing his first professional contract in the summer of 2013. He was a regular for the Reading U18 and U21 teams; however, he never played competitively for the club and was released in May 2016.
Leeds United
Following a successful trial, Shaughnessy was given a one-year contract with the Leeds United development squad in September 2016. But he did not make any first team appearances during the 2016/2017 Season. His contract was extended by a year in In May 2017, and he made his professional debut in a 3–2 away victory over Bolton Wanderers on 6 August 2017, replacing injured teammate Matthew Pennington at centre back in the 66th minute and promptly giving away a penalty. He made his first start in the following game, on 9 August 2017 in a 4–1 League Cup victory against Port Vale at Elland Road, and first League start six days later against Fulham. He signed a new four-year contract with Leeds the following month. On 7 January 2018, Shaughnessy scored an own goal in Leeds' 2–1 shock defeat to Newport County in the FA Cup. Shaughnessy picked up a serious ankle injury when he started in Leeds' 0-0 draw against Hull City on 30 January 2018, with head coach Thomas Christiansen revealing Shaughnessy could spend several weeks/months out injured. The injury ultimately ruled Shaughnessy out for the remainder of the season. On 14 August, Shaughnessy returned to a match-day squad for the first time, when he was named on the bench for Leeds in the Carabao Cup fixture against Bolton Wanderers. He made his first appearance after injury when he started against Preston North End on 28 August. The return to form - and from injury - of Leeds' back line has limited Shaughnessy's playing time with the first team, but a revealing interview in September 2018 shows that manager Marcelo Bielsa has firm plans for the youngster in this 2018/19 campaign and beyond.
On 7 January 2019, Shaughnessy joined Hearts on a 6 month loan deal. He made his debut on 20 January starting for Hearts in a 1-0 win against Livingston in the Scottish FA Cup, before making his league debut on 23 January in the SPL against Dundee. On 25 May 2019, Shaughnessy received a 2018–19 Scottish Cup Runners Up medal after being named on the bench for the Scottish Cup final at Hampden Park after losing 1-2 in the final against Celtic. In total he made 11 appearances for Hearts in all competitions.
On 2 September 2019, Shaughnessy joined League Two side Mansfield Town on a season long loan after failing to break into Leeds Head Coach Marcelo Bielsa's immediate plans.
After his loan at Mansfield was ended early, Shaughnessy signed on loan for League One club Burton Albion on 13 January 2020 for the rest of the 2019–20 season.
International career
Shaughnessy has represented Ireland at U15, U16, U17, U18 and U21 level. After his loan move to Hearts he expressed his hopes that he would get a senior international call up similarly to fellow Irish under 21 centre back Jimmy Dunne who he replaced at Tynecastle.
Personal life
Shaughnessy's elder brother Joe is also a professional footballer and plays for League One club Southend United.
