Navarro, who did have a headache and had trouble eating on Thursday, was not in the starting lineup Friday.
"My head was really painful," Navarro said. "It was like a switch turned off. Good thing I am a baseball player, not a boxer. I am fine right now and it was nothing really serious."
As a precautionary measure, manager Joe Maddon will rest Navarro for the next few days.
"He is going to be available emergency-wise tonight and then he will be available [Saturday]," Maddon said. "I am expecting [Raul] Casanova to at least catch the next two days. Today and tomorrow and maybe even the next day, too, I am not sure yet. Of course, if he comes into tomorrow and he is just doing cartwheels, then we might reconsider, but it might be Sunday when he is able to play."
Navarro was admitted to a hospital on Thursday. After he was evaluated and released, Navarro, still in his uniform, rode a taxi to the team plane and changed into his suit.
"The main thing was my head," Navarro said. "They did some tests and some X-rays. My vision was a little messed up. I told them I was fine, but they wanted to make sure everything was all right. I am fine now."
No rotation set: Maddon has not finalized his post-All Star-Break rotation quite yet. The manager talked with executive vice president Andrew Freidman before Friday's game against Kansas City about the pitching, but no set plans were reached.
Edwin Jackson would pitch the first game back if the Devil Rays stayed on their normal rotation. The problem lies in the doubleheader against the Yankees on Saturday, July 21.
"That is part of the concern," Maddon said.
Injury updates: Maddon still hopes that B.J.Upton, who has been on the 15-day D.L. since June 14 with a left quad strain, will return to the Devil Rays on Thursday, the day after the All-Star break ends.
Because Class A Vero Beach was rained out on Thursday, Upton will play Friday through Monday, get Tuesday off and might have to play on Wednesday for Vero.
"The original plan called for him to be off Tuesday and Wednesday," Maddon said.
Upton will see action at second base, center field and designated hitter.
Shawn Riggins, DL'd since June 4 with right elbow tendinitis, will DH on Friday night in a rehab assignment for Class A Vero Beach. Upton will play in the field Friday.
"Riggans is throwing better, his arm is feeling better," Maddon said.
Josh Paul, placed on the 60-day DL with a left elbow strain on May 24, could start a rehab assignment as soon as the All-Star break ends.
"We are anxious to get JP back here also, because from a pitcher's perspective, I think he does a lot of important stuff for us that often goes unnoticed," Maddon said. "I thought he was playing at a very high level prior to his injury."
Closer Al Reyes, who has missed the last three games with a rotator cuff strain, threw before Friday's game. He is hoping to throw off flat ground Saturday and "hopefully" throw off a mound after the All-Star break.
"It's getting better," Reyes said.
Pitching coach Jim Hickey, out since June 25 to fix a detached retina after a golfing accident, should rejoin the team Saturday.
Howell learns: J.P. Howell said he took several steps after his disastrous two-thirds of an inning, six-run performance Thursday against the Red Sox. The outing continued a three-start stretch that has seen the left-hander's ERA rise from 4.26 to 6.62.
"I have handled things well," he said. "Before, I would worry about things a little more. I understand it a long season now. I never knew what forcing it was until [Boston] and I never understood it."
Howell, like Shawn Camp, also returned to familiar grounds. The duo each pitched for the Royals before joining the Devil Rays. Howell, a former KC first-round pick, was in the trade that sent Joey Gathright and Fernando Cortez to the Royals on June 20, 2006.
"Always nice to come back to his place," Howell said. "The hospitality, they still have it and always will."
Jennings earns award: Class A Columbus outfielder Desmond Jennings was named the Devil Rays' Minor League Player of the Month for the second time this season. In June, Jennings hit .378/.441/.671 (batting average/on-base percentage/slugging percentage) with 13 stolen bases, four homers and 18 RBIs. Jennings, the Devil Rays' 10th-round pick in the 2006 First-Year Draft, is batting .317 with 37 stolen bases this year.
Quotable: "It's all good. We are trying to make this right and we shall make this right. It's difficult right now and I understand that, however I am not changing my viewpoints one bit. I know we are going in the right direction, but things have conspired against us for the moment, but we will eventually come out on top." -- Maddon, on the team's 11-game losing streak, the longest team's skid since Aug. 27-Sept. 10, 2004 .
Devil Rays report: Triple-A Durham lost, 3-0, to Buffalo. Jae Seo fell to 2-3 for the season after allowing two runs in five innings of work. Seth McClung threw two hitless innings, struck out three and walked two. He has a 1.45 ERA this season. Outfielder Justin Ruggiano (.848 on-base plus slugging percentage) was named to the International League All-Star team in place of Jeff Niemann, who will pitch in the Futures Game during the All-Star Break. ... Double-A Montgomery beat Mobile. Chris Mason tossed five innings of one-run ball and lowered his ERA to a Southern League-best 2.51. Dale Thayer improved to 7-0 with a 1.66 ERA after throwing five outs of shutout relief. ... Reid Brignac went 2-for-5 with his ninth homer this season. Class A Vero Beach was postponed because of rain.
Class A Columbus defeated Charleston, 8-7. Brian Baker collected his fifth save of the season and tossed two scoreless innings. He has 47 strikeouts and a 40/13 strikeout-to-walk rate this season. ... Short-season Hudson Valley was postponed because of rain. ... Rookie League Princeton won, 2-1, over Johnson City. Chris Andujar went six innings and permitted one run. Justin Garcia earned the save after throwing one inning. He has thrown three scoreless innings for Johnson City this summer.
Coming up: Andy Sonnnastine (1-3, 5.63 ERA) will face Royals ace Gil Meche (5-6, 3.26 ERA) on Saturday night at Kauffman Stadium. First pitch is set for 6:10 p.m. CT.
Conor Nicholl is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.