The bombings, which injured several players in a nearby housing complex, occurred as two Syrian clubs were preparing to train in Tishreen Stadium
Sleman's club Al-Wathba and Hama-based Al-Nawair, both of whom compete in Group 1 of the Syrian Premier League, were set to train at Tishreen Stadium when mortar rounds struck near where the players were staying.
"We were collecting our things about to head to the stadium when we heard the first explosion and the windows were blown off," Al-Wathba forward Ali Ghosn told the Associated Press. "We ran out to the corridor when the second explosion struck and I saw Yussef fall down bleeding from the neck."
Sleman's death was one of the latest in the ongoing conflict, which has claimed over 70,000 lives as rebels seek to overthrow President Bashar al-Assad. With security in the country a serious concern, Syria's national team has been forced to play all of its recent fixtures outside the country.