Royals 4, Giants 2: Billy Butler belted a two-run homer and added the go-ahead RBI single in the sixth inning as host Kansas City recorded its fifth straight victory.

Alex Gordon added an RBI single and Omar Infante matched Butler with two hits for the Royals, who improved to a major league-best 13-3 since July 22 and remained 2 1/2 games behind first-place Detroit in the American League Central. Jason Frasor (3-1) struck out two in one scoreless inning of relief to pick up the win as Kansas City maintained its one-half game lead for the second wild card.

Joaquin Arias ripped an RBI double and Matt Duffy recorded a run-scoring single for the Giants, who fell to 4-4 on their 10-game road trip but remained 3 1/2 games behind the first-place Los Angeles Dodgers in the National League West. Madison Bumgarner (13-9) fell to 9-3 away from home after permitting four runs - three earned - on seven hits in eight innings as San Francisco maintained its share of the second wild-card spot.

Butler deposited a 2-2 fastball from Bumgarner over the wall in left-center field to give Kansas City a 2-0 lead in the first inning. San Francisco forged a tie in the third before the Royals rebounded in the sixth as Butler plated Infante with a single to right and Gordon followed with a base hit to left to score Salvador Perez.

Kelvin Herrera and Wade Davis each worked a scoreless inning to bridge the gap to Greg Holland, who struck out a pair in the ninth for his 33rd save.

GAME NOTEBOOK: Butler, who improved to 11-for-19 in his last five games, passed Danny Tartabull for seventh place in franchise history with his 125th homer. ... Royals LHP Jason Vargas yielded two runs on nine hits in five innings to settle for a no-decision. ... San Francisco placed 1B Brandon Belt on the seven-day concussion disabled list prior to the contest. He had just returned from the DL on Saturday after a concussion sidelined him for 12 games.