In 1933, National League president John Heydler issued a memo to team presidents recommending against inter-team fraternization. By the end of the decade, Commissioner Kennesaw Mountain Landis had turned it into law. Umpires were tasked with sitting in the stands before games and taking names of those players willing to converse across borders, with fines levied against the guilty.

Because those mores were in line with the unwritten rules, not many fines were needed. Heck, in the 1965 All-Star Game, Bob Gibson wouldn’t talk to his own catcher, Joe Torre, because they played for different teams during every other game of the season.

“When I had the uniform on, somebody with the other uniform, I wanted to choke them,” said 1993 AL Cy Young Award-winner Jack McDowell. “I wanted to kill them. I’m sure as hell not going to go shake their hands and talk to them, even warming up before a game.”

These days, that mindset has faded, for one primary reason. “There’s interaction now,” said Dusty Baker. “High school games, section games, college games, Area Code games, Junior Olympic team, Olympic team, Pan Am Games—most of these guys know each other, and for a long period of time before they even get to the big leagues.”

Even with that in mind, Melky Cabrera tried to push the envelope following his fourth-inning homer in Tuesday’s All-Star Game. As San Francisco’s center fielder rounded first, he spied one of his best friends in the game, Yankees second baseman Robinson Cano. The pair had come up together through New York’s minor league system, and remain close.

As Cabrera approached second, he held out his hand to slap five with his pal—who, it should be re-stated, was playing for the other team.

How did it sit? Not well in Cabrera’s own clubhouse, likely. His manager for the day, Tony La Russa, is known to have some feelings on the subject. From Buzz Bissinger’s Three Nights in August: “It drives [La Russa] crazy when a hitter gets a single and starts chatting it up with the first baseman as if they’re distant cousins at a family reunion. He shares the fan’s view that it simply doesn’t look good: Baseball is meant to be a game of competition, not a game of whassup dog?”

Whassup dog, however,  seemed to be on Cabrera’s mind. Cano refused to play along. (Watch it here.)

“He tried to give me a high five, and I know this is the All-Star Game, but I don’t want to look bad out there,” Cano said in a CBS Sports report. “It was fun, and if it was a closer game I might be having fun. I didn’t want to upset my teammates. We’re playing to win.”

It’s doubtful that Cabrera would have tried such a thing anyplace but an exhibition, but it was still an odd and awkward sight.

“Take ’em out to dinner,” said pitcher Dick Bosman of such encounters. “Sit in the lobby of the hotel. But whatever you do, you’re not supposed to be doing it out there on the field.”