Ronaldo had two goals ruled offside in his return to for Corinthians, which was held to a scoreless draw with Guarani in the Brazilian league on Sunday to extend its winless streak to seven matches.
The result did little to quell the pressure from fans disappointed with the team's recent struggles, but kept the popular club within striking distance of leader Cruzeiro, which lost 2-1 to Gremio in Porto Alegre.
With eight rounds to go, Cruzeiro has 54 points, one more than second-place Fluminense and four more than Corinthians. Fluminense was held to a 0-0 draw with Botafogo.
Ronaldo, playing for the first time in 10 matches, had his goals disallowed in close calls in the 5th and 20th minutes at the Brinco de Ouro da Princesa stadium in Campinas. Both times he positioned himself just in line with Guarani defenders and easily found the net, but the linesman each time said the striker was a step ahead of his opponents. TV images showed Ronaldo appeared to be onside for at least one of the goals.
The 33-year-old Ronaldo was still far from his best, but posed a constant threat to Guarani. His best chance to score came from a close-range header that went just wide in the 71st.
"That really was a missed chance," Ronaldo said. "We also had the two goals disallowed, but overall it was a good return."
It was only Ronaldo's fourth match in the Brazilian league this year. The three-time FIFA player of the year hadn't played since Sept. 8, when he scored in a 1-1 draw with Atletico Paranaense.
About 200 fans attended Corinthians' training session on Saturday to protest against Ronaldo, demanding that he improve his physical condition and stop using Corinthians as a personal "spa."
Ronaldo's veteran teammate Roberto Carlos also was far from his best Sunday and was substituted in the second half.
Corinthians, seeking their first national league title since 2005, hasn't won since a 3-2 victory at Santos on Sept. 22. The team is without a coach since Adilson Batista quit after a defeat last Sunday, but president Andres Sanchez said he expects to close a deal to sign veteran manager Tite on Monday.
Cruzeiro missed a chance to increase its league lead despite scoring first against Gremio at Olimpico stadium.
Argentine playmaker Walter Montillo scored in the 28th, but Gremio rallied with goals by Junior Vicosa in first-half injury time and by league-leading striker Jonas from a penalty kick in the 75th - his 20th goal.
The result extended Gremio's unbeaten streak to eight matches and moved the two-time national champion to seventh place. Cruzeiro hadn't lost in four matches.
Fluminense could have taken over the lead had it beaten Botafogo at Engenhao stadium, but it failed to do better than a draw in the matchup between Fluminense Argentine playmaker Dario Conca and Botafogo Uruguay striker Sebastian Abreu.
Also Sunday, right back Jean scored three minutes into second-half injury time to give Sao Paulo a 4-3 win over fourth-place Santos at Morumbi stadium. The six-time champion got the win despite playing a man down from the 58th after midfielder Richarlyson was sent off for a hard foul.
Atletico Mineiro defeated Avai 2-0 in Minas Gerais, while four-time champion Palmeiras - without injured Chile playmaker Jorge Valdivia - was held to a 1-1 home draw with Ceara. Palmeiras midfielder Marcos Assuncao scored his fourth free-kick goal in the last six matches.
In Salvador, Colombian goalkeeper Julian Viafara scored from a penalty to help Vitoria beat last-place Prudente 2-0.
On Saturday, defending champion Flamengo defeated Internacional 3-0 to move six points from the relegation zone. Former Fenerbahce striker Deivid scored two goals for Brazil's most popular club, which has won two of the three matches under the command of Vanderlei Luxemburgo.
In Curitiba, Atletico Paranaense beat Goias 2-1 with goals by midfielder Branquinho and Paraguayan midfielder Ivan Gonzalez.
