Smith's first hit with the Padres came on a 2-0 pitch from Brian Wilson, who started the eighth after Hyun-Jin Ryu threw seven scoreless innings. It sailed an estimated 360 feet into the right-field seats. It was his seventh career pinch-hit homer. He was acquired in an off-season trade with Oakland for reliever Luke Gregerson.
Wilson (0-1) walked pinch-hitter Yasmani Grandal, who advanced when the veteran reliever couldn't handle Everth Cabrera's bunt for an error. Grandal stole third and Cabrera took second on indifference before Denorfia hit a bouncer up the middle to bring them both in.
Dale Thayer (1-0) pitched a perfect eighth for the win. Huston Street finished for the save.
The defending NL West champion Dodgers had started the regular season with a two-game sweep of the Arizona Diamondbacks in Sydney.
Ryu got the start after reigning NL Cy Young Award winner Clayton Kershaw was scratched due to a swollen back muscle and then placed on the 15-day disabled list for the first time in his seven-year career.
In a scheduling quirk, the left-hander started consecutive regular-season games. He made his season debut a week earlier, when the Dodgers beat the Diamondbacks in their second game in Australia.
Ryu retired 16 in a row from the second inning until one out in the seventh. He then walked rookie Tommy Medica, who was then erased in a 3-6-3 double play.
Ryu allowed three hits, struck out seven and walked three.
The Dodgers grabbed the lead on a nice piece of hitting by Carl Crawford with two out in the fifth.
Crawford went the other way with an 0-2 pitch from Andrew Cashner, hitting it over third baseman Chase Headley to bring in Dee Gordon from second. Gordon had reached on a walk and advanced when Cashner fielded Ryu's bunt and forced A.J. Ellis at third.
Cashner allowed four hits in six innings. He struck out five and walked two.
NOTES: The Padres renamed the broadcast portion of the press box the Jerry Coleman Broadcast Center in memory of the Hall of Fame broadcaster who died on Jan. 5 at 89. His widow, Maggie, and daughter, Chelsea, threw out the ceremonial first pitches. Coleman won four World Series titles with the Yankees and was the only major leaguer who saw combat in both World War II and Korea, flying a combined 120 missions as a Marine Corps pilot. He was a Padres broadcaster for four decades. ... Sunday night's attendance of 45,567 set the Petco Park single-game record. ... Padres manager Bud Black said LF Carlos Quentin's time on the disabled list will go beyond April 10, when he'd be eligible to be activated. He was placed on the DL on Saturday, retroactive to March 25, with a bone bruise in his left knee. Quentin was hurt diving for a ball in a spring training game. ... Rookie Tommy Medica started in LF for the Padres. He made his big league debut with the Padres in September. ... Monday is an off day. Tuesday's scheduled starters are Zack Greinke for Los Angeles and Ian Kennedy for San Diego.