Kemp homered early and Los Angeles hammered a struggling Santana before holding off the New York Mets 7-6 on Friday night.
Luis Cruz connected for his first major league home run off Santana (6-7), who entered 5-0 with a 0.50 ERA in five career starts against the Dodgers. That included eight innings of three-hit ball in a 5-0 win June 30 at Los Angeles, but the two-time Cy Young Award winner has hit the skids hard since then.
''We know what Johan's capable of. We hopped out on him early, worked counts and got good pitches to hit and kind of made him pay for his mistakes,'' Kemp said. ''Usually he's hitting spots and his stuff is a little bit better. I just think he was a little off today.''
Santana was pulled after three innings and fell to 0-3 with a 13.50 ERA in his last three starts, the worst three-game stretch of his stellar career. After missing last season following shoulder surgery, he is 3-5 with a 6.54 ERA in eight outings since throwing a career-high 134 pitches June 1 against St. Louis to finish off the first no-hitter in Mets history.
''That no-hitter stuff was a long time ago,'' Santana said. ''I'm OK, just not able to execute. I feel OK. I don't feel my best right now.''
Mets manager Terry Collins said the team would discuss options with Santana about how to get some ''energy'' back in his arm, and a stint on the disabled list is a possibility.
''He's not hurt,'' Collins said. ''We're going to talk about some alternatives as soon as I'm done in here. Skipping a start, backing him up some - those are some of things we are going to discuss.
''He just hasn't responded,'' the manager added. ''It's a command issue. He's not making the pitches.''
In addition to the two-run homers by Kemp and Cruz off Santana, the Dodgers got RBI singles from Jerry Hairston Jr. and Juan Rivera to back Aaron Harang (7-5), who allowed one earned run in five innings.
Rookie pinch-hitter Jordany Valdespin socked a two-run homer off Shawn Tolleson in the seventh to trim New York's deficit to 7-6.
''It was a battle tonight, you know?'' Dodgers manager Don Mattingly said. ''Seemed like we couldn't get away. Felt like everything I did didn't work out. It was just one of those games.''
Javy Guerra got out of the inning, however, and Ronald Belisario threw a called third strike past David Wright with a runner on to end the eighth.
Kenley Jansen worked a scoreless ninth for his 17th save. With a runner on second, he struck out pinch-hitter Justin Turner and retired Andres Torres on a popup to end a game that took 3 hours, 41 minutes in an intermittent drizzle.
''It was nice to get the offense going out early,'' Andre Ethier said. ''Wish we could have figured out a way to have it continue and kind of put them away instead of letting them back in the game like that.''
Four of Valdespin's six homers have come as a pinch-hitter, tying Mark Carreon (1989) and Danny Heep (1983) for the club's single-season record. Daniel Murphy had a season-high four hits for New York, including two doubles.
Hairston made a tough play at third base to deny his brother, Scott, a leadoff single in the eighth.
The Mets, who snapped a six-game losing streak Thursday in Washington to salvage the final game of a 1-5 road trip, have lost eight of 11.
Ethier doubled and scored twice for the Dodgers, who opened a 10-game road trip with their second straight victory following a 1-7 slide. He also got his second stolen base of the season and scored on Rivera's seventh-inning single to make it 7-4.
Bobby Abreu opened the game with an infield single and Kemp, who hit a game-ending homer Wednesday against Philadelphia for his first long ball in 17 games since April 30, went deep for the second consecutive at-bat.
''I feel my legs getting under me. I feel better. I feel pretty good at the plate,'' said Kemp, who missed 51 games with a strained left hamstring during two stints on the disabled list before returning last Friday. ''I feel like my normal self.''
Hairston, who was 0 for 18 against Santana, made it 3-0 with an RBI single.
Santana walked three batters with two outs in the second, and Ethier's four-pitch pass with the bases loaded made it 4-2. Cruz, filling in for injured shortstop Dee Gordon, drove a 1-2 pitch to left in the third to make it a four-run game.
The home run ball was retrieved for Cruz so he can keep it as a memento.
''I'm very happy. Today is a big day for me,'' Cruz said. ''That guy is one of the best pitchers in the league.''
Santana threw 72 pitches in three innings. The 33-year-old left-hander yielded six runs on seven hits and has given up 19 runs, 28 hits and six homers over 12 2-3 innings in his past three outings.
Until his previous game at Atlanta, Santana had never given up six runs in consecutive starts. Now he's done it three times in a row.
''I'm just going through a tough time. I'm not on top of my game right now,'' Santana said. ''After everything I've been through, I'm very happy to take the mound every five days. I just have to keep working, battling, competing.''
NOTES: Dodgers RHP Chad Billingsley, on the DL since July 8 because of inflammation in his right elbow, was scheduled to throw a bullpen session at Citi Field. Mattingly said he's ''pretty confident'' Billingsley will be able to start Monday in St. Louis. ... New York will recall RHP Jeremy Hefner from Triple-A Buffalo before Saturday's game.