"That's the Matt Kemp we used to play against,'' he said.
Kemp's two-run homer led surging San Diego past the San Francisco Giants 4-2 on Monday night at Petco Park.
San Diego won its fifth straight game, its longest winning streak of the season. The Giants had their six-game winning streak halted.
Kennedy (5-9) claimed his first victory since June 18, snapping a four-game skid. He pitched six innings and was charged with two runs on six hits and a walk. He struck out six and hit a batter.
"I had good fastball command,'' he said. "I was getting ahead of guys early on and I was pitching off that.''
Craig Kimbrel threw a four-pitch ninth for his 26th save in 27 chances.
Giants starter Tim Hudson (5-8) was working his first game since June 26 after a disabled-list stint. In his first outing since turning 40, Hudson worked four-plus innings and allowed three runs on five hits and four walks.
"I wasn't quite as sharp as I would have like to been, especially with my fastball command,'' Hudson said. "I was falling behind in the count, a lot of walks, a lot of hitters' counts, having to pitch out of a lot of traffic pretty much from the first inning on.''
Manager Bruce Bochy agreed: "He was off, it was pretty evident early in the game. He was battling his command and trying to get on track. He was not sharp.''
The Padres have defeated the Giants in 13 of their past 18 games at Petco since 2013.
Kemp's two-run blast in the third was the key blow and extended his season-high hitting streak to eight games. It was the Padres' sixth homer in three games.
"He's really come on,'' interim manager Pat Murphy said of Kemp. "Now he's the best player on the field.''
The Padres padded their lead to 4-2 in the sixth when third baseman Yangervis Solarte collected his third single, this one driving in center fielder Melvin Upton Jr. Upton opened the frame with a triple to right-center.
The Padres grabbed a 3-2 lead in the fifth inning when second baseman Jedd Gyorko's sacrifice fly off reliever Yusmeiro Petit scored Solarte. But the Padres left the bases loaded.
The Giants had tied the game at 2-2 in the fifth, as catcher Buster Posey's RBI single drove in second baseman Joe Panik. Panik had singled and advanced on third baseman Matt Duffy's base hit.
Kennedy, who had lost four straight starts, wiggled from a jam in the fourth inning.
Alexia Amarista booted right fielder Hunter Pence's one-out grounder, the third error by a Padres shortstop in two days. First baseman Brandon Belt walked, but Kennedy retired shortstop Brandon Crawford and left fielder Gregor Blanco.
Hudson tiptoed around trouble in the first. But the 40-year-old couldn't escape Kemp in the third.
Following Amarista's one-out walk, Kemp hit his 10th home run of the season. It gave Kemp his 700th career RBI and the Padres a 2-1 advantage.
"To be honest with you it's been Matt's emergence as a leader that has allowed everyone to relax,'' Murphy said. "It's really great to see."
The Giants struck first in the second inning when Blanco smacked a 91 mph Kennedy fastball for a solo homer, Blanco's third of the year.
NOTES: Padres LF Justin Upton wasn't in Monday's lineup after exiting Sunday with a tightness in his back. ... RHP Brandon Morrow (shoulder) threw a simulated game and could go on a rehab assignment this weekend. ... Alexi Amarista started at shortstop, one day after Will Middlebrooks committed two errors in 4 2/3 innings at shortstop. ... Giants RHP Tim Lincecum, who is on the DL with a strained forearm, had an MRI on his sore hips, and the tests revealed degenerative issues. He'll resume throwing in five days. ... RHP Tim Hudson (shoulder) was activated from the DL to start Monday's game. ... RHP Jean Machi was designated for assignment.