Ashcraft (5-7) allowed two runs on five hits with three strikeouts and two walks. Ian Gibaut fanned two batters in a scoreless seventh inning, and Lucas Sims bridged the gap to Alexis Diaz, who struck out two batters in the ninth to secure his 27th save of the season.
The Reds mustered just four hits en route to posting their first win since an 8-5 triumph over the Milwaukee Brewers on July 8. Cincinnati will bid for a split of the current four-game series on Thursday afternoon
San Francisco's Blake Sabol belted an opposite-field homer to lead off the seventh inning. Sabol recorded two of the six hits for the Giants, who saw their seven-game winning streak come to a halt
Cincinnati's Christian Encarnacion-Strand, who was playing his third major league game, and Tyler Stephenson each singled to open the third inning.
Benson stepped up and deposited a 1-0 slider from Ross Stripling (0-3) over the left-center-field wall to give the Reds a 3-0 lead. The homer was Benson's sixth of the season and second in as many days
The Giants loaded the bases in the fifth when David Villar was hit by a pitch and the next two batters walked. Villar scored as Joc Pederson grounded into a double play, and Ashcraft induced Mike Yastrzemski to pop out to end the threat
Sabol halved San Francisco's deficit by sending a 3-1 cutter from Ashcraft over the wall in left field. The homer was Sabol's 11th of the season and first since he went deep on twice against the Seattle Mariners on July 3.
Stripling was saddled with the loss after permitting three runs on four hits in six innings. He fanned two without issuing a walk.
--Field Level Media