The 4-2 victory against the A's moved them to within 2 1/2 games of the AL wild card lead.
Oakland has won 12 of 14 to improve to 31-45 and move within four games of first in the American League West.
The Giants scored 43 runs in the series, to move within two games of the .500 mark.
With the victory, the Pirates moved within five and a half games of the Mets.
A victory Tuesday would have moved them within two games of Phoenix, the team with the best record in the league, in the loss column.
The resurgent Red Sox move within 5 games of the Yankees with the win.
The Cardinals moved within two games of the lead with their seventh victory in 11 games.
The Mets won the opener, 1-0, to move within two games back with five remaining to play.
They have moved within two games of the Marlins in the National League East.
Boston moved within three and a half games of Detroit.