Mark is one of two central defenders signed on loan from Liverpool during the 1980s, the other being Nicky Tanner. Mark's spell at Anfield generated England Youth caps but no first team appearances and so he sought to move his career elsewhere. He joined Norwich on loan in November 1986 and made his debut in place of the injured Tony Spearing against Coventry. He also played against Oxford and Everton but a reserve team booking took him over his disciplinary point limit and led to a suspension and ultimately the end of his Carrow Road career. He had failed to justify a permanent move and Norwich switched their attentions to Ian Butterworth.

Mark joined Manchester City for £100,000 the following summer and made 42 league appearances for them. A back injury in January 1989 forced him out of first team contention resulting in a transfer to Bolton Wanderers in September 1990. A first team regular at Burnden Park, Mark made 157 league appearances for Bolton before joining Swindon Town where he partnered Ian Culverhouse.

Mark's 1997/98 season was been blighted by injury and resulted in Mark being granted a free transfer in May 1998. He has since rejected a contract offer from Carlisle United and has joined GM Vauxhall Conference side Barrow. His place at Barrow was threatened by the club's perilous financial position. Chairman Stephen Vaughan resigned following the start of a fraud squad investigation into the club's recent share issue in October. Vaughan's share holding and the freehold of the stadium have been put up for sale. The complete playing squad was transfer listed after a FA Umbro Trophy defeat at Hucknall Town only added to their woes. (Source: Team Talk magazine, January 1999) The March 1999 edition of Team Talk magazine showed that Mark has been released by the poverty stricken club. The April edition reported that Mark had joined Runcorn of the Unibond Premier League.

Mark later joined Third Division Blackpool as Assistant Manager to his former Swindon boss Steve McMahon.

On 2nd June 2006, Mark joined Premiership side Wigan Athletic as first team coach. He had played with Wigan manager Paul Jewell in Liverpool's reserve team

In November 2007, Mark joined Jewell at his new club Derby County. Unfortunately Derby were relegated to the Championship on 29th March 2008

Mark left Derby in December 2009/Janaury 2009 following the resignation of Jewell and the appointment of Nigel Clough as Derby's manager.

Seagraves re-united with Jewell again in November 2011 when he joined Jewell's Ipswich Town team as a scout along with Andy King

In May 2013 Seagraves began working in Delhi India, for a company called "India On Track" in conjunction with Arsenal Soccer Schools. He is working to create a structure within the Soccer Schools that will be sustainable and will ensure the future development of football and football players within India