The former World Player of the Year's first attempt was saved by Nacional goalkeeper Ignacio Don with a spectacular dive to his right in the 13th minute.
The 33-year-old was given another chance five minutes later, this time following a handball, and made no mistake as he chose the opposite corner and put the ball out of Don's reach.
However, he was upstaged when Marco Riveros equalised for the rank outsiders by chipping a majestic free kick over the Mineiro wall eight minutes before halftime.
Mineiro, unbeaten after four games, stayed top of Group Four on eight points, three ahead of their opponents who are second.
Mineiro's fellow Brazilians Gremio, also unbeaten, scored a stoppage time equaliser to draw 1-1 at Newell's Old Boys in Group Six as they stayed top.
Third-placed Newell's, semi-finalists last season under current Barcelona coach Gerardo Martino, twice hit the woodwork before Maxi Rodriguez finally put them ahead in the 78th minute.
Gremio looked down and out until Rhodolfo came to their rescue when he headed a dramatic equaliser in the 91st minute to silence the crowd at the Marcelo Bielsa stadium.
Flamengo completed a winless evening for Brazilian teams when they sank to a 1-0 defeat at 3,600 metres above sea level in La Paz against Bolivar, leaving the 1981 winners bottom of Group Seven on four points.
Juan Carlos Arce converted a penalty for the Bolivian side, third on five points, in the fourth minute following a blunder by Flamengo defender Samir, who slipped as he tried to play the ball out of defence before hauling down William Ferreira.
Mexico's Leon (seven points) went top of the group by beating Ecuadorean champions Emelec 3-0, with Matias Britos, Jose Vazquez, from a penalty, and Carlos Pena sharing the goals.
Five-times winners Penarol brought their campaign to life by scoring twice in the last 20 minutes to beat Arsenal 2-1 for their first win in Group Eight at the fourth attempt.
Ivan Marcone put the Argentine visitors ahead with a long-range strike early in the second half before Luis Aguiar volleyed home the equaliser for the Uruguayans and Jonathan Rodriguez grabbed the winner with nine minutes left.
- Sports & Recreation