The rookies were major contributors Thursday, helping the defending AL East champions rally twice in extra innings to beat the Toronto Blue Jays 7-6.
Jennings' solo homer in the 10th made it 4-all. Chirinos tied it again in the 11th with a two-out, pinch-hit single up the middle against Shawn Camp (1-2) and then won it with another two-out single in the 12th.
A third rookie, right-hander Brandon Gomes (1-1), pitched one scoreless inning for his first major league win.
"Those guys are showing they definitely belong in the big leagues," Rays designated hitter Johnny Damon said.
"It's not like we have to wait for them to be good. I feel very confident in them," manager Joe Maddon added. "Obviously, they lack experience. Obviously they need to be tested in even hotter moments than today. But I think they can achieve in those moments because their makeup is so good, combined with their skill level."
The Rays said Chirinos became the first rookie with separate tying and winning hits in extra innings of the same game since Nick Green did it for the Atlanta Braves against the Boston Red Sox on July 2, 2004.
Slumping slugger Evan Longoria, who entered the day on a 3-for-33 slide that dropped his batting average to .226, hit a three-run homer for Tampa Bay. Jose Bautista hit his major league-leading 33rd home run for Toronto, a solo shot off Wade Davis that made it 3-all in the eighth.
"It was a tough game. We jumped out quick, got a couple of runs but didn't have many opportunities for six straight (innings)," Blue Jays manager John Farrell said. "Jose hit the home run to get the game back tied and ... pump some life back into us."
The Blue Jays took a brief lead in the 10th when Colby Rasmus delivered a RBI double for his biggest hit since being acquired from the St. Louis Cardinals in an eight-player trade on July 27. Reliever Jon Rauch blew a save chance in the bottom half when Jennings hit a leadoff homer.
In the 12th, Chirinos liked his chances.
"He was the one in trouble," Chirinos said, describing the final at-bat against Camp. "He had to throw strikes. ... You win and you see everybody smiling and happy, it's just a great feeling."
It was a difficult loss for the Blue Jays, who had a chance to win three consecutive series for the first time since mid-May.
"I think any time you lose a game late, those are tough to take," Farrell said. "You work all day to get yourself into a position, you present yourself the position and it is not converted."
Longoria homered off Blue Jays starter Brett Cecil to erase a 2-0 deficit in the fifth.
Davis, meanwhile, got off to a shaky start for the second straight outing. He gave up five first-inning runs at Oakland last week but then settled down and didn't allow any more over the next five to give the Rays a chance to rally to beat the Athletics.
The Blue Jays loaded the bases with no outs in the first when Rasmus doubled and Davis walked Escobar and Bautista. Adam Lind's single, snapping a career-worst 0-for-22 streak, drove in one run and another scored when Edwin Encarnacion grounded into a double play.
Cecil limited the Rays to one hit -- Casey Kotchman's two-out single in the fourth -- until Justin Ruggiano and Jennings singled in the fifth. Damon kept the inning going by hustling up the first base to avoid grounding into a double play, setting up Longoria's first-pitch homer that put the Rays ahead 3-2.
The Rays have especially struggled offensively at Tropicana Field. While they lead the majors in runs scored on the road with 294, they're 29th at home with 177. They matched their season high at the Trop with nine in a 9-1 victory over Toronto on Wednesday night but remain one of two AL teams that have yet to score 10 or more in a home game this season. ... Rays right-hander Jeff Niemann starts the opener of a weekend series against Oakland on Friday night. He went 3-0 with a 1.06 ERA in five starts in July. His ERA during the month ranked second in the majors to CC Sabathia's 0.92. Niemann is 2-0 with a 1.59 ERA and one shutout lifetime against the Athletics. ... Left-hander Brad Mills will make his second start of the season for Toronto when the Blue Jays continue their six-game road trip at Baltimore on Friday. He lost his season debut 3-0 to the Texas Rangers, allowing two runs over seven innings. ... The Blue Jays purchased the contract of infielder Brett Lawrie from Triple-A Las Vegas. In addition, left-hander Luis Perez was recalled from Las Vegas, outfielder Travis Snider was optioned to the Triple-A club and right-hander Carlos Villanueva was placed on the 15-day disabled list with a right forearm strain.