Tejada, acquired Thursday from the Baltimore Orioles, started at shortstop for the first time this season and went 0 for 3 with a walk.
LeBlanc has allowed a team-high 16 homers, 11 in his last seven starts.
Ross homered into the second deck in left-center with two outs in the fourth, his 10th, to give the Marlins a 3-1 lead. Sanchez homered to left with one out in the sixth, his 12th, to make it 4-1.
The Marlins got their first two runs in the third on Hanley Ramirez's sacrifice fly and Logan Morrison's RBI single.
Chris Volstad (5-8) allowed two runs and seven hits in five-plus innings, walked three and struck out one.
Leo Nunez pitched the ninth for his 25th save in 30 chances.
LeBlanc (5-9) allowed four runs and five hits in 6 1-3 innings, struck out five and walked two.
LeBlanc had two singles but was erased both times when Jerry Hairston Jr. hit into double plays.
Hairston singled leading off the Padres' first and with two outs, stole second with Tejada batting. Tejada walked and Chase Headley singled to bring in Hairston. Headley rounded first too far and was caught in a rundown when the Marlins cut off the relay throw home. Tejada then broke for home, was caught in a rundown and tagged out.
The Padres pulled to 4-2 in the sixth when Chris Denorfia hit a leadoff triple to right-center and scored on Adrian Gonzalez's single to left. Gonzalez was thrown out trying to take third on Headley's grounder to short.
NOTES: Marlins manager Edwin Rodriguez said there's a chance LF Chris Coghlan, on the DL with a torn meniscus in his left knee, could play again this year. Coghlan, the 2009 NL Rookie of the Year, was hurt while delivering a pie to the face of teammate Wes Helms during a post-game celebration on Sunday. Rodriguez said Coghlan will keep receiving treatment to see if the swelling and pain go down. If it doesn't, surgery would be likely. ... LeBlanc picked off his seventh baserunner this year, second behind Mark Buehrle of the Chicago White Sox.