League leader Fluminense was held to a 2-2 draw by rival Vasco da Gama in Deco's return to Brazilian football on Sunday.
The result in front of 80,000 fans at Maracana stadium cut Fluminense's lead to two points after second-place Corinthians remained unbeaten against Sao Paulo in more than three years with a 3-0 win.
Also Sunday, young striker Neymar scored one goal and set up another in his first match since rejecting a multimillion euro offer from Chelsea, helping Santos beat Vanderlei Luxemburgo's Atletico Mineiro 2-0, and Chile playmaker Jorge Valdivia made his return to Palmeiras in a 0-0 draw with Guarani.
Defender Gum opened the scoring for Fluminense with a seventh-minute header, but Vasco - which had won two in a row - rallied with goals by striker Eder Luis in the 38th and defender Fagner in the 58th.
Left back Julio Cesar took advantage of a sequence of mistakes by Vasco defenders to score from close range in the 60th, extending Fluminense's unbeaten streak to 12 matches.
Deco came off the bench in the 75th and had a chance to score what could've been the winner in the 87th, but his shot from in front of the goal went over the crossbar.
The Brazil-born playmaker left Chelsea to sign a two-year contract with the Rio de Janeiro club to fulfill a longtime dream to return after 13 years in Europe. He had played only two matches with Corinthians before moving to Benfica and eventually FC Porto in Portugal. He then excelled with Barcelona and ultimately Chelsea.
A member of the Portuguese national team until retiring from the squad after the 2010 World Cup, Deco was Fluminense's top signing as it tries to win its first Brazilian championship since 1984. Led by three-time Brazilian champion Muricy Ramalho, Fluminense has 33 points from 15 rounds.
Four-time champion Corinthians moved closer with a pair of first-half goals by midfielder Elias at Pacaembu stadium. Brazil midfielder Jucilei added the third in the second half to keep Sao Paulo winless from three matches and near the relegation zone with only 17 points.
Sao Paulo hasn't beaten Corinthians in 10 matches, since 2007.
At Vila Belmiro stadium, Neymar scored on a penalty kick in the 58th and sent a perfect through ball for Danilo's goal in the 79th to help Santos beat Atletico Mineiro 2-0 just three days after rejecting a ?35 million offer from Chelsea and extending his contract with the Brazilian club until 2015.
The 18-year-old striker on Thursday decided to stay with Santos instead of moving to the Premier League even though his agent said Chelsea was willing to cover his buyout clause, which under the new contract was increased in ?10 million to ?45 million.
Neymar is one of the most talked-about players in Brazilian football in recent years. He made his debut in the Brazilian national team earlier this month, scoring a goal in Brazil's 2-0 win over the United States in a friendly in New Jersey.
Luxemburgo's Atletico Mineiro dropped to the relegation zone with its 10th loss in 15 matches.
Chile star Valdivia, in his first match since rejoining Palmeiras after playing nearly two years in the United Arab Emirates, came off the bench at halftime but was not able to help Luiz Felipe Scolari's team win its third in a row.
The four-time national champion, which played a man down from the 75th after a sending off, is only 12th in the standings, 13 points off the lead.
Four days after winning the Copa Libertadores, Internacional's second-stringers were held to a 1-1 draw with last-place Atletico Goianiense in Porto Alegre, while defending champion Flamengo fell 1-0 to Atletico Paranaense in Curitiba to drop to 10th on the table.
On Saturday, Botafogo reached third place with 24 points by beating fifth-place Avai 1-0 in front of about 35,000 fans at Engenhao stadium in Rio. It was the fourth consecutive victory for the team led by former South Africa coach Joel Santana.
In Fortaleza, fourth-place Ceara scored a late goal in a 2-1 victory against struggling two-time national champion Gremio, which also is in the relegation zone. The bottom four clubs are demoted.
Prudente, which had three points deducted from its total for illegally using a player without proper documentation, rebounded by beating second-to-last-place Goias 2-1 in Goiania. Goias missed a penalty in the 89th.
