"I'm just not very good right now," said Marquis, who walked two and struck out four. "I'm not able to make consistent pitches like I want. Obviously, they're squaring balls up a little better than I hoped. Whether it's bad location or not, as much life on the ball I would like, I've got to figure out something here quick because it's not fun."
Marquis fell to 3-3 with a 6.63 ERA in his seven starts and has allowed nine home runs, including five in his last two starts. In his back-to-back losses, he's also given up 11 earned runs and 17 hits.
The San Francisco first inning began with a leadoff walk to Gregor Blanco and Joe Panik's single. With two outs, a first pitch to Brandon Belt was launched a projected 421 feet by Statcast™ to right field for a three-run homer.
"It was a sinker, in," Marquis said. "[Catcher Brayan] Pena said it was pretty decent in. He just got the barrel to it and was able to keep it fair and not hook. He was able to stay inside the ball a little better than we anticipated."
The Giants notched four hits in the third inning, including Buster Posey's two-run homer to left field. There was also a walk and a drive to the center-field warning track that was caught.
Reds manager Bryan Price feels Marquis has been making location mistakes lately and getting behind in counts. He also said his sinker and changeup haven't been as effective.
"They've been tumbling out of his hand a little bit early," Price said. "He's missing with the changeup that's staying on the arm side, away to lefties and in to right-handers. The fastball command of the bottom of the zone and working ahead hasn't been as consistent as it was earlier.
"I know he's working hard on it. I tried to make an adjustment with his mechanics between starts … just to stay back and give himself time to gather and get out in front with his stuff. He just wasn't able to find it today."
Mark Sheldon is a reporter for MLB.com. Read his blog, Mark My Word, follow him on Twitter @m_sheldon and Facebook and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.