Playing the final game of his illustrious career, former Australia international Kewell was unable to inspire his side to victory at AAMI Park, meaning the Heart are guaranteed to end the regular season bottom of the table.
Western Sydney, meanwhile, can look forward to a week off and a home semi-final after late goals from Brendan Santalab and Youssouf Hersi earned a hard-fought triumph.
Nikolai Topor-Stanley headed the Wanderers into a 27th-minute lead from Shinji Ono's free-kick, but the Heart swiftly levelled through Orlando Engelaar.
Western Sydney's victory was crucial given that Central Coast Mariners and Melbourne Victory also recorded victories on Saturday.
Victory cruised to a 4-1 triumph at 10-man Wellington Phoenix, with Archie Thompson's first-minute strike setting the tone.
James Troisi and Guilherme added further goals for Kevin Muscat's men prior to half-time, and Mark Milligan scored from the penalty spot in the 59th minute after Shaun Timmins had been sent off for bringing down Kosta Barbarouses.
