Greško began his career at Dukla Banská Bystrica in 1995, before he was signed by Inter Bratislava in 1997 where he played until 1999.

On 5 May 2002, during the last week of the 2001–02 season, Greško headed the ball to Karel Poborský, allowing him to score in a 2–4 defeat against Lazio.

He spent only eighteen months between November 2000 and June 2002, making a total of 41 league appearances.

[10][11] During the 2004–05 campaign, he suffered a cruciate ligament damage in December which led to him not playing for the rest of the season.

In July 2007, Greško returned to Bayer Leverkusen as a free agent on a two-year contract after nearly seven years.

In March 2011, he joined Slovak club ŽP ŠPORT Podbrezová (promoted to the second league 2011–12 – the second highest team event in Slovakia), Where he received a one-year contract in July 2011.