SEATTLE (Interstat) — Gavin Sheets homered twice and drove in three runs as the San Diego Padres completed a three-game sweep of the Seattle Mariners with an 8-3 victory Sunday afternoon at T-Mobile Park.

Sheets launched a solo shot in the first inning off Mariners starter George Kirby and added a two-run homer in the sixth as part of a five-run outburst that broke the game open. He finished with three hits, including a double, and scored three times as San Diego improved to 28-18. Seattle dropped to 22-26.

Lucas Giolito earned his first win of the season for the Padres, allowing three runs on one hit over five-plus innings. He walked four and struck out two before being relieved after Seattle’s three-run sixth. Kirby took the loss, falling to 5-3. He surrendered seven runs on six hits over five-plus innings, striking out six and walking two.

The Padres struck first in the opening inning. After Fernando Tatis Jr. grounded out and Miguel Andujar grounded out, Sheets connected on a 1-2 pitch and drove it over the right-field wall for his eighth homer of the season. San Diego added a run in the fifth when Ty France singled home Xander Bogaerts, who had walked to lead off the inning.

The game turned decisively in the sixth. With one out, Andujar doubled sharply to center. Sheets followed with his second homer, a blast to right that made it 4-0. Manny Machado doubled, Jackson Merrill doubled to drive in Machado, and France capped the rally with a two-run single, giving the Padres a 7-0 lead.

Seattle answered in the bottom of the inning. Giolito lost his command, walking Colt Emerson, Leo Rivas and Julio Rodriguez to load the bases. Josh Naylor walked to force in Emerson, and Randy Arozarena and Rob Refsnyder followed with sacrifice flies, scoring Rivas and Rodriguez. That cut the deficit to 7-3, but Giolito struck out Cole Young to end the threat.

San Diego added an insurance run in the seventh. Tatis singled, moved to third on Andujar’s groundout and scored on Sheets’ double to left-center off reliever Alex Hoppe. That made it 8-3.

Seattle managed only one hit in the game — a second-inning single by Luke Raley off Giolito. The Mariners struck out 11 times, including three in the ninth as San Diego reliever Bradgley Rodriguez closed it out. The Padres collected 10 hits, with France adding two singles and two RBIs. Machado and Merrill each doubled.

The attendance was 40,365. The game lasted 2 hours, 54 minutes.

San Diego won the first two games of the series 7-4 on Saturday and 2-0 on Friday. The Padres have won four of their last five overall and open a three-game home series Monday against the Los Angeles Dodgers. Seattle returns home Monday to host the Chicago White Sox for a three-game set.

Interstat’s game simulator had projected a final score of San Diego 6, Seattle 5. Interstat’s ELO system gave Seattle a 51.70 percent probability to win. Seattle was installed as a pregame favorite with a spread of minus-1.5. The total of 11 runs went under the over-under line of 7.5.