Waterford born John O'Shea joined Manchester United after spending summers travelling to England to train with the Academy. He signed professional terms with United in August 1998 and made his first team debut just over a year later, away to Aston Villa in a Worthington Cup defeat. 

After making twenty appearances and scoring two goals for the Reserves over the 1998/99 and 1999/2000 seasons, John joined Second Division Bournemouth on loan in January 2000, making his League debut for the Cherries against Colchester United.

Some assured displays earned John rave reviews on the south coast, with Bournemouth. He could play on both sides of the defence, displayed composure under pressure and played with assurance and confidence on the ball.

After ten starts and one goal, against Millwall, O'Shea returned to Old Trafford in March 2000, determined to break into the first team. Despite two more appearances in the Worthington Cup, away at Watford and Sunderland, it didn't quite happen for him, so he embarked on another loan spell in season 2000/01.

This time he followed in the footsteps of Luke Chadwick, Danny Higginbotham and Ronnie Wallwork by joining United's Belgium associates, Royal Antwerp. Although he was first choice central defender for the Belgians, he still found time to play international football for the Republic at Under-21 level.



John stepped up to earn his first senior cap on 15 August 2001, when he came on as an 84th minute substitute at home to Croatia. Unfortunately, the debut ended in disappointment when John gave away a penalty in injury time, enabling the visitors to make the score 2-2. He returned to the United reserves and made a handful of impressive appearances for the first team in late 2001, most notably against Lille and Boavista.


2002-2003 was a season which began with Rio Ferdinand grabbing the headlines, but John O'Shea ended up stealing the critical acclaim. It was the break-through season in the Irishman's career as he establish himself into the first team. With the squad hit by numerous injuries to defensive players early in the campaign, John was forced into the limelight earlier than Sir Alex planned. However, all at Old Trafford were highly impressed by his excellent performances and adaptability.

The versatile O'Shea was able to play at left, right back or in the centre of defence. United fans enjoyed his talent for pulling off swerves and step-overs and he was particularly effective down the wing in an attacking role. This was especially true in the 6-2 win at Newcastle but fans will also remember his audacious nut-meg of Luis Figo at Old Trafford.

By the end of the season he had played in 52 games and become a solid fixture in the Reds defensive line-up. Many even went as far to suggest he was United's player of the season and he was indeed nominated for the PFA Young Player of the Year.

Season 2003-2004 was a difficult second season for John with expectation's now a lot higher than previous. And with Rio Ferdiand's suspension causing havoc amongst United's defenders his form took a dip. Yet the Irishman remained a regular in the first team starting 32 league games and scoring twice which included the winner at home to Wolves. 



 The following year O'Shea found his left back position under pressure from the new arrival Gabriel Heinze. He had to make do with more appearances as sub, although coming off the bench he scored with a clever 20 yard lob in the 4-2 win at Highbury over Arsenal. The Irishman also found himself playing in central midfield as a defensive holding player.

John reverted to defensive duties for season 2005-2006 due to the injuries that ruled out both Gabriel Heinze out and Wes Brown. By the end of the campaign with the arrival of Vidić and return of Brown, the Irishman was back in the midfield holding role, forming an unlikely but surprisingly successful central partnership with Ryan Giggs. Only Rio Ferdinand played in more games that O'Shea that season.



In 2006-2007 he was injury free and featured in 48 games (27 starts and 22 as substitute). The Irishman featured more at the right back position than in central midfield but he also served as an emergency goalkeeper.

On February 4, 2007, during league game against Tottenham Hotspur, O'Shea deputised for Edwin Van Der Sar in goal after the latter was taken off the pitch for a broken nose, and Manchester United had already used all three substitutes. During this time he denied his Republic of Ireland teammate Robbie Keane a goal with a save a few minutes before the end of the game (following this incident, United fans chanted "Ireland's number one" in O'Shea's honour). 

A month later he won over many United fans by scoring an injury time winner at Anfield for United in the league, having come on as a substitute for Wayne Rooney. This goal was important in United going on to regain the Premiership trophy for the 2006/2007 season.

John O'Shea scored on 80% of his shots in the 2006-2007 season.