"I just saw it come off the bat hot, and when it hit him I knew it hit him hard," said Ryan Roberts, who was in the on-deck circle for Tampa Bay. "I instantly started praying for him. That's a situation you never want to see. It's unfortunate. I hope he recovers and hope he's back pitching as soon as possible. That's something in a game you hate to see."
Jennings left the clubhouse without speaking to reporters.
Toronto manager John Gibbons stood on the mound as Happ was strapped to a backboard and immobilized. The left-hander was lifted onto a stretcher and wheeled off the field through an opening behind home plate.
"That was a real scary moment," Rays manager Joe Maddon said. "That was awful. I hope that he's well."
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.
Happ's injury was the latest to a pitcher struck by a batted ball during the last few years, and Major League Baseball has discussed ways to protect hurlers on the mound.
"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 told the AP in an email after Happ was injured Tuesday night. "Some of the products are promising. No company has yet developed a product that has satisfied the testing criteria."
Oakland right-hander Brandon McCarthy was hit in 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 the hospital six days later.