Bayfront Medical Center said in a statement that Happ was discharged after being upgraded from fair to good condition on Wednesday. Happ was taken there after being struck on the left side of the head by a ball off the bat of Desmond Jennings during Tuesday night's game against the Tampa Bay Rays.
The Blue Jays said Happ was responsive and feeling better after sustaining a head bruise and cut to his the left ear.
"I'm in good spirits," Happ said in a statement released by the hospital. "I definitely appreciate the support of the baseball community. It's been overwhelming, the messages and kind words I've been getting. I just want to thank everyone for that, and I look forward to getting back out there soon."
Happ's frightening injury at Tropicana Field left players on both teams shaken and revived questions about whether Major League Baseball is doing enough to protect pitchers, who often find themselves in harm's way on the mound.
The pitcher raised his glove in front of his face as quickly as he could, a futile attempt to shield himself from the batted ball headed straight for his temple.
It was too late. Thwack!
The sickening sound of a sharply hit baseball striking his skull was heard all the way up in the press box.
And then, sheer silence.
Happ, hit squarely in the second inning during Toronto's 6-4 victory, was immobilized on a backboard, lifted onto a stretcher and wheeled off the field.
It was the latest injury to a pitcher struck by a batted ball in the last few years, and baseball has discussed ways to protect hurlers who ply their craft against the world's strongest hitters - only 60 feet, 6 inches from home plate.
General managers discussed the issue during their meetings in November and MLB presented several ideas at the winter meetings weeks later.
MLB staff have said a cap liner with Kevlar, the material used in body armor for the military, law enforcement and NFL players, is among the ideas under consideration.
The liners, weighing perhaps 5 ounces or less, would go under a pitcher's cap and help protect against line drives that often travel over 100 mph.
"We are actively meeting with a number of companies that are attempting to develop a product, and have reviewed test results for several products," MLB spokesman Pat Courtney wrote in an email to The Associated Press after Happ was injured. "Some of the products are promising. No company has yet developed a product that has satisfied the testing criteria."
Several pitchers around the majors sounded resistant - even after seeing replays of Happ's injury.
"You know the risks," Angels lefty C.J. Wilson said. "Guys get hurt crashing into fences. Guys get hurt tripping over first base and blowing their knee out. This is professional sports, and we are paid well to take those risks."
MLB could implement the safety change in the minor leagues, as it did a few seasons ago with augmented batting helmets, but would require the approval of the players' union to make big leaguers wear them.
"It wouldn't be hard for me," De La Rosa said. "To protect against those kinds of things, it's good for us."
"The game's been played a long time. Situations like that are unfortunate, but we have to keep it our game," he said. "I don't think you have to adjust the whole program."
And Seattle Mariners right-hander Aaron Harang thought it would be difficult for veteran major league pitchers to adapt to new equipment.
"I know it's a hot topic," he said, "but I don't think it's a problem that's easily solved. I know a lot of people want pitchers to start wearing helmets. It's a good idea in theory, but I don't know how practical it is. I think you need to start with that at the lower level, I'm talking high school and maybe even lower, and then gradually introduce it into the higher level. I've been pitching since I was 6 years old and I've never worn a helmet. I think it would be tough to make that adjustment while pitching in a major league game."
Texas Rangers manager Ron Washington wondered if there's a viable solution.
"What can you do?" he said. "Tell hitters not to hit it back up the middle?"
Oakland right-hander Brandon McCarthy was hit on the head by a line drive last September, causing a skull fracture, an epidural hemorrhage and a brain contusion that required surgery. He was released from a hospital six days later.
McCarthy, who pitched for Arizona on Tuesday night against the Los Angeles Dodgers, said he won't watch video of Happ getting hit.
"I don't know what the GMs and the owners have to do with anything. It's not like they're pitching," McCarthy said. "Until someone makes something that works, it's going to be tough for someone to wear it.
"Most everything that's come out wouldn't have protected me, and it wouldn't have protected (Happ) if he got hit directly in the ear. You're at a point now where you're looking at batting helmets. You'd have to have something that protected the ear and then the face and beyond. So it's kind of a slippery slope. Someone will have to come up with something really good and really sound. Otherwise, I don't know how you answer that question."
Still, McCarthy maintains hope.
"We've put things on the moon before, so I feel like we can create some sort of a device that sits over your head and protects you," he said. "Someone will do it. It's just a matter of when, not if."
Jennings' liner caromed off Happ's head and halfway up the right-field line in foul territory as Jennings raced around the bases for a two-run triple. The 30-year-old Happ dropped face down at the front of the mound, holding his head with his glove and bare hand.
Team trainers, paramedics and medical officials rushed to Happ's aid as a stunned crowd of 10,273 at Tropicana Field fell into a horrified hush. A shaken Jennings stood with his hands on his head, and other players were visibly concerned as they watched Happ receive medical attention for about eight minutes.
The pitcher was wheeled off the field to a waiting ambulance. Just before he disappeared under the stands, Happ raised his right hand and waved. He received a standing ovation from the crowd, and the game resumed after an 11-minute delay.
"I came in and watched it and I wish I wouldn't have," Mariners pitcher Joe Saunders said after looking at the video. "It was ugly. It was scary. I just hope he's going to be all right."