Perhaps spurred on by the tension of the moment, Youkilis immediately charged the mound and threw his helmet toward Porcello. Youkilis and Porcello then dragged each other to the ground. From there, both benches and bullpens emptied in a game the Red Sox went on to win, 7-5.
Youkilis and Porcello were both ejected and are all but certain to be disciplined by Major League Baseball.
Consider that Miguel Cabrera, the Tigers' star slugger, had been hit by Brad Penny in the fourth inning of Monday's game, and again by Red Sox righty Junichi Tazawa in the first inning on Tuesday. Cabrera had to leave Tuesday's game in the second inning, thanks to lingering soreness in his left hand from the pitch Tazawa hit him with.
"It's baseball," said Tigers catcher Gerald Laird. "Miggy's a big slugger in the middle of our lineup, and you've got to protect your sluggers. Today, that wasn't intentional, but that's the second time they hit him, and they hit two guys yesterday. That's just part of the game."
No sooner had Cabrera exited the game than Youkilis got hit by Porcello with the very first pitch in the bottom of the second inning. And this all happened one night after Tigers right-hander Edwin Jackson had nailed Youkilis.
"A ball came up high at my numbers and it looked like there was intent there," said Youkilis. "With two days in a row of getting hit, at some point you have to do something to protect yourself as a hitter. I had enough of it. I felt like I had to do what I had to do."
Porcello denies throwing at Youkilis.
"The only thing I have to say about tonight is that I was not intentionally throwing at Kevin Youkilis," said Porcello. "That's all I have to say. It was unintentional. There was nobody on. It's a 3-0 game. I was not trying to hit him intentionally."
Even if the Tigers didn't think Cabrera was hit on purpose by Tazawa, they were irritated that their star was put in harm's way.
Moments after he was hit in that top of the first, Carlos Guillen took an aggressive takeout slide into Red Sox second baseman Dustin Pedroia in his successful attempt to break up a double play. Manager Terry Francona immediately came out and argued with second-base umpire Scott Barry, but to no avail.
In the bottom of the first, Red Sox first baseman Victor Martinez gestured at Porcello after taking a pitch high and tight that nearly hit him.
"The one in the first inning with Martinez, it's just to show them, 'You're gonna pitch inside, we're gonna pitch inside.' That's just the way it is," said Laird. "It's baseball, and today it just got a little out of hand."
Martinez wasn't amused at all to have a pitch come so close to nailing him.
"You know what? I think they really misunderstood what was going on," said Martinez. "We were never trying to hit Cabrera. If you see the video, those pitches, you could tell they weren't on purpose. We understand their reaction. They're protecting their big guy and that's what it's all about."
The Red Sox also don't like seeing Youkilis -- a key cog in their lineup -- getting hit.
"If I was Youk, I don't think I'd be too happy getting smoked two days in a row either," said third baseman Mike Lowell, who replaced Youkilis in the game and hit two homers.
It was the first time Youkilis has charged the mound.
"A lot of times guys are trying to pitch inside," said Youkilis. "There's times you get hit, but I think the past two days were different. There was intent there to hit."
Porcello -- coincidence or not -- has hit two batters this season. Both times, it has been Youkilis.
"I knew I was out of the game -- it's a given," said Youkilis. "I just walked off the field. It was over with, you're done, you're out of the game -- this is something I've never done before and never thought of ever doing, but I lost my control there and let my emotions get the best of me."
Now, he will find out what his punishment is.
"I'm sure something will happen," said Francona. "We'll just wait and see. Youk's a real good player and his versatility makes him even better for us, but we have guys [to fill that spot]. You don't want to lose any players, but I'm sure something will happen."
"I definitely regret it being on TV with the kids out there," said Youkilis. "That's not the way you should handle it, but there comes a point in your life where you have to protect yourself -- you can't just continue to get hit up there."
Francona was ejected later in the bottom of the second by Barry for arguing when J.D. Drew was called out trying to steal second.
Ian Browne is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.