After walking the first batter he faced, and one more in the first inning, Lamet struggled with his control most of the game, but did manage to strike out eight. Lamet's bout of wildness follows his last start against Philadelphia, in which he walked one over seven innings and picked up his fourth straight win.
"I think the key to the game today was me not being able to command that fastball, and having to rely on my slider too much," Lamet said through a translator.
Including Sunday, Lamet has allowed three hits or fewer in his last six starts.
"I'm always trying to limit that, but at the same time I'm not trying to avoid contact, so I can get deeper into the game."
Lamet showed poise in the third after allowing a double to Wilmer Difo and issuing a pair of walks, but recovering to strike out Anthony Rendon with the bases loaded, limiting the damage to one run.
"When you look at him, there is a lot to like," Padres manager Andy Green said. "Even the fight to him, punching out [Rendon] with the bases loaded, he did some good things."
While Lamet did not surrender a hit until the third, and only allowed three hits total, the 25-year-old right-hander let the game slip away in the fifth when he walked opposing starter Gio Gonzalez to lead off the inning. He scored on a Daniel Murphy sacrifice fly.
Lamet lost for the first time since July 18, a span of five starts, but Green had two perspectives on his young starter's performance.
"There are two different ways you can look at it," Green said. "One, you realize how good he can be, walking six guys and effectively giving up one run. Very few pitchers can do that against a good lineup -- his stuff is that good. On the flip side, you can't walk six guys and expect to win baseball games."
Green also lamented Lamet's lack slider usage when his fastball command was clearly off.
"When he gets off with his fastball, his slider gets him back on," Green said. "Today, for some reason he stayed fastball-dominant for a long period of time. The way he uses the slider gets him back in line, but he struggled. You appreciate his stuff and his fastball, but at the same time he has to mix it up as well."
The Padres' offense did little to support Lamet, as Gonzalez held San Diego at bay over 6 2/3 innings. Gonzalez yielded one run on five hits opposite Lamet, and struck out eight Padres batters.
"[Gonzalez] has been great all year, and his command is as good as I've seen it," Green said. "He pitched well, but in reality, and I think you saw this all series, they gave us opportunities to beat them early, with some mistakes. If you want to beat good pitchers, you have to capitalize on mistakes. We didn't do that."
Tim Powers is a contributor to MLB.com based in San Diego.