SAN DIEGO -- Fernando Tatís Jr. says he fell ill with the COVID-19 virus several days ago, which meant he had to watch the party from his couch while the San Diego Padres clinched a playoff spot Monday.

When he returned to the Padres' lineup Friday after missing three games, Tatís made sure the baseball world knows he's healthy and ready for October.

Tatís hit a grand slam in the fourth inning of the Padres' 7-4 victory over the Arizona Diamondbacks on Friday night, swinging the momentum in a win that kept San Diego in contention for a home playoff series.

"I feel way better today, and I'm looking forward to feeling even better in the next couple of days," Tatís said after his fourth career grand slam.

Tatís missed the Padres' entire home series with the Milwaukee Brewers earlier this week after coming down with the virus. His teammates took two of three from the team with the best record in the majors, including an 11-inning victory Monday that secured back-to-back playoff berths for San Diego for only the second time in franchise history.

While the Padres popped bottles and drenched their clubhouse, Tatís was jealous.

"It's definitely hard watching from home," Tatís said. "We've played for this all year, so (I) definitely was looking forward to that celebration. But now that means we need to celebrate a couple more times."

Tatís did his part to keep the party going Friday when he connected off Arizona's Zac Gallen for his 24th homer of the season, erasing a 2-1 deficit. The five-tool star known as El Niño stood at the plate and admired his 409-foot shot while another sellout crowd at Petco Park roared for him.

"Welcome back Tatí, right?" Padres manager Mike Shildt said. "I mean, he's always had power. There was a spell where he didn't do it, but I think we feel good about him (being) a dangerous guy regardless of the power included."

Tatís' illness interrupted a productive season in which he hasn't been a dominant power hitter, but has demonstrated a consistency and a durability that eluded him in earlier years. He has driven in 70 runs for the third time, but he's done it with career bests of 157 hits and 109 runs while playing in a career-high 153 games and counting.

Tatís also homered against the White Sox last Sunday in the Padres' final game before his illness.

Thanks to Tatís' slam and reliever Mason Miller's four-out save, the Padres (88-72) remained in contention to host the Chicago Cubs (90-70) in their wild card series next week -- although San Diego can only avoid that trip to Wrigley Field if it wins both of its weekend games against Arizona while the Cubs lose twice to St. Louis.

No matter where the clubs meet, Tatís is feeling confident in the Padres' chances of making another playoff run -- and in his own chances of continuing his impressive postseason play.

He has shown off his power stroke in his two previous trips to the postseason, hitting six homers and driving in 12 runs in his 13 career playoff games. His career postseason OPS is a whopping 1.328.

"I feel like I'm in a great place," he said. "Playoff baseball is definitely different, and I'm looking forward to that adrenaline."

Fernando Tatís Jr. returns from bout with COVID-19 to hit a grand slam in the Padres' playoff push