Once a virtual lock to make the playoffs, the Philadelphia Phillies will enter the final day of the regular season with their postseason hopes still up in the air.

The Phillies (87-74) can clinch their fifth straight postseason berth on Sunday afternoon when they host the American League East champion Tampa Bay Rays (98-63) in the regular-season finale for both teams.

Right-hander Zack Wheeler (13-5, 3.06 ERA) will try to rescue the Phillies, who have lost four games in a row, all on nights in which they could have clinched a National League wild-card berth. Philadelphia not only lost each of those contests, but the Arizona Diamondbacks (86-75) -- the Phillies' lone remaining competition for the NL's final playoff spot -- have been hot for the past week.

Arizona had won six straight games before falling 10-7 to the San Diego Padres on Saturday. That brought Philadelphia's magic number to one heading into Game 162.

In four starts this month, Wheeler is 2-0 with a 1.75 ERA. He struck out 11 batters in 5 2/3 innings against the Milwaukee Brewers on Tuesday in his last start, allowing three runs and five hits in a no-decision in the Phillies' 6-4 victory.

"I feel like he's getting better every time out," Phillies interim manager Don Mattingly said of Wheeler, who struck out the first seven Brewers he faced and crossed the 2,000-strikeout plateau for his career.

Wheeler has faced the Rays five times in his career, going 2-2 with a 4.11 ERA.

"We're always confident when that guy's on the mound," catcher J.T. Realmuto said after Saturday's setback.

Tampa Bay will start right-hander Nick Martinez (15-5, 2.94 ERA), who gave up two runs over six innings in a 2-0 loss to the New York Yankees on Tuesday in his most recent outing. Martinez struck out a season-high seven batters but still suffered his first loss in more than a month, giving up a two-run homer to Cody Bellinger in the fourth inning after Ben Rice had doubled.

"Two pitches that leaked back over the plate, and they were back-to-back pitches," Rays manager Kevin Cash said. "But Nick did everything else really, really incredibly well, as usual."

Martinez is 0-1 with a 3.31 ERA in six lifetime games (one start) against the Phillies. On Sunday, he will face a lineup that has a total of three runs over the last four games.

"You might think I'm crazy, but tonight ... our guys fought the whole way," Mattingly said following Saturday's 12-1 loss to the Rays. "... I was actually encouraged at the end of that game. Maybe I'm being overly optimistic, but I was encouraged tonight."

Richie Palacios drove in four runs, and Victor Mesa Jr. had four hits and two RBIs to highlight Saturday's win for Tampa Bay. Other standouts for the Rays included Junior Caminero, who slugged his 42nd homer, and Yandy Diaz, who collected three hits and scored three runs.

Caminero, who is expected to finish in the top five of the American League MVP voting, will complete his 162-game season when he takes the field Sunday.

"It's amazing. What a feat," Martinez said.

Caminero and the Rays already have earned a first-round bye in the playoffs and will face the winner of the wild-card series between the Yankees and Boston Red Sox.

"We keep fighting every single day," Caminero said. "Every game matters for us."