PEORIA, Ariz. ? Mike Sweeney homered in his first at-bat Tuesday after missing four games because of tightness in his lower back.

Sweeney hit the two-run homer — his team-leading fifth home run — in the first inning off San Diego Padres’ left-hander Sterling Hitchcock. The Royals won, 9-4.

“I feel healthy,” Sweeney said. “I feel great. My swing is right where I want it. I just want to stay healthy and take it into the season.”

Sweeney’s health remains a major concern for the Royals because he missed 54 games last season because of back problems and a herniated disc.

“I feel strong and confident that I’m going to be healthy,” Sweeney said. “I keep doing my back exercises and doing my part, and just pray to God for good health. The rest is out of my hands.

“I was bummed I missed the last few games because of my back, but what can you do?”

Sweeney drove in a franchise record 144 RBIs in 2000, but the four-time All-Star first baseman has not had 100 RBIs in a season since.

He has been working with hitting coach Jeff Pentland on fine-tuning his stroke.

“I was able to execute what we’ve been working on on the home run,” Sweeney said.

Benito Santiago hit a three-run homer in the first and drove in four runs in the Royals’ victory. Santiago’s single in the third scored Juan Gonzalez, who had doubled.

Left-hander Jeremy Affeldt retired the final 10 batters he faced after yielding a run in each of the first two innings to pick up the victory. Affeldt, 2-0, allowed two runs on four hits and one walk over five innings.

Greg Swindell, who had been out because of a groin pull, pitched a flawless seventh for the Royals in his first appearance since March 15.

Royals left-hander Jimmy Gobble, who strained an abdominal muscle last week, threw 36 pitches in a bullpen session Tuesday, his first time on the mound since the injury.

“I felt no immediate pain,” Gobble said after the session. “They want to see how it feel tomorrow. Anything can linger after you get done throwing.”