Marcel netted both goals as 2011 AFC Champions League quarter-finalists Suwon Bluewings handed second-placed Pohang Steelers a rare defeat in the K-League.
There were just three minutes on the clock when Marcel gave Suwon the lead, the Brazilian striker heading in a cross from Yeom Ki-hoon, but Pohang drew level on the stroke of half-time.
A low shot from Kim Jae-sung from outside the area seemed hopeful until it deflected off the leg of Suwon defender Mato Neretljak and past the wrong-footed Jung Sung-ryeong.
However, it was to be Marcel's day as he scored his side's winner midway through the second half when his low left-footed shot from the edge of the area squeezed under Shin Hwa-yong in the Pohang goal to seal Suwon's third successive victory.
Pohang's defeat, only their second of the season, means that leaders Jeonbuk Motors can go seven points clear on Sunday.
Elsewhere, Jeju United won 4-2 at bottom club Gangwon FC. Kim Eun-jung and Lee Hyun-ho put Jeju 2-0 ahead and while Gangwon hit back through Lee Eul-yong and Kim Yong-hu to make it 2-2, Jeju took the points thanks to a second goal from Kim and a late strike from Brazilian star Santos.
Daejeon lost a three-goal lead as they drew 4-4 with Chunnam Dragons.
Daejeon raced into a 3-0 lead by the midway point of the first half thanks to two goals from Han Jae-woong and one from Han Deok-hee.
However, a brace from Chunnam's Brazilian striker Wesley either side of the break put his side back in the game while Lee Wan made it 3-3 just before the hour.
Daejeon striker Wagner, another Brazilian, looked to have grabbed the winner 11 minutes from time as he made it 4-3 but Lee Byung-yoon scored in the last minute to earn a point for Chunnam.
Daegu FC fought back from an early deficit to win 2-1 at Sangju Sangmu, first-half goals from Kim Min-gu and Kim Hyun-sung cancelling out Kim Jung-woo's strike to give Daegu the spoils.
In the other games, Busan I'Park defeated Seongnam Ilhwa 1-0 thanks to a goal from Han Sang-woon while Incheon United drew with Gwangju FC 2-2. Park Jun-tae and Jeon Jae-ho got the goals for Incheon while Kim Dong-seop and Jaoa Paulo scored for the visitors.