Billy Wagner knows one of baseball’s golden rules is never letting hitters peek behind the pitcher's curtain, but he could never help himself when it came to Bobby Abreu. 

The two were teammates coming up in the Astros minor league system and later as established big leaguers in Philadelphia, and both players shared plenty of trade secrets from their established polarized positions as shutdown pitcher and versatile hitter. Many conversations on bus rides with Triple-A Tucson back in the summers of 1996 and 1997 — and then later on upgraded chartered jets with the Phillies in 2004 and 2005 — evolved into each player picking the other’s brain about the secret language of baseball.

Wagner marveled at Abreu’s ability to set up opposing pitchers and lull them into throwing the pitch he wanted in certain situations. Abreu, who now plays right field for the Angels, shook his head at Wagner’s embarrassment of pitching riches — including a 97 mph fastball and a moving, diving slider that served as the ultimate wipeout pitch — and the way Wagner overpowered hitters with sheer stuff.

As expected, Wagner and Abreu’s baseball insider trading approach eventually came back to bite the 38-year-old left-hander during one-on-one matchups against the ultimate pitch-grinding offensive machine. That happened again in Sunday afternoon’s Red Sox loss when Abreu hit a hard ground ball down the first base line that had trouble written all over it.

Abreu’s ball bounced off the webbing of Kevin Youkilis’ glove and landed in the photographer’s pit for a ground-rule double, and the Halos were off and running in the eighth.

The two-base hit led to a pair of earned runs added to Wagner’s postseason ledger and cracked the door open for Anaheim’s Sunday afternoon revival in Game 3’s stunning turnaround. It also led to Wagner jokingly cursing out Abreu after the season’s final, bitter defeat. It was with good reason. Abreu torched Sox pitching for a .556 batting average in the three-game series, was on base nine different times and scored four runs while routinely pushing Boston pitchers beyond their pitch limits -- and Wagner has seen this story way too many times before.

“I know him really well,” Wagner said. “We came up together in Houston and then we played together in Philly. We’re good friends. I’ve told him the last two times that he’s gotten hits off me that I hate him. I just say, ‘I hate you.’ All of the times that I’ve picked it up for him, and he’s gotten a hit against me in every single way possible.”

“He knows its part of the game and that’s it. People are going to hear that and think, ‘Oh, controversy’, but Bobby is just going to laugh. I’ve known him for a long time. He’s been like that his whole career. I think people seem to all of a sudden be noticing him, but he’s been doing this his whole career. He’s always been a really tough hitter and somebody that it’s fun to compete against. He deserves it. He’s been in Philly and New York. He survived.”

The unconventional Abreu double greeted Wagner right out of the chute in the eighth, and the lefty reliever sandwiched a Vlad Guerrero walk between a Torii Hunter strikeout and a Kendry Morales groundout.

“We made some pretty darned good pitches to [Abreu], but he was able to put the bat on the ball,” Wagner said of Abreu, who went 3-for-5 Sunday. “He’s what hurt us [this series].”

That was it for Wagner, who couldn’t wriggle his way out of trouble in the frame and needed Jonathan Papelbon to clean up. Papelbon gave the first morsel of evidence that it was going to be a rough afternoon when he surrendered a hit that scored both Angels baserunners, and suddenly Los Angeles was given new life.

“I don’t know why [Papelbon] should get all the blame,” Wagner said. “If I go out there and give him a 1-2-3 inning then it saves him from going out there for that third [of an inning]. You don’t want to put your closer in that situation.

“It sure is easier when you have one inning to pitch rather than having to come in and clean up somebody else’s mess.”

The two earned runs stemming from his “mess” also pushed Wagner’s career postseason ERA over 10.00, and didn’t do anything to dissuade criticism that Wagner simply isn’t a playoff performer.

Wagner’s teammates clearly weren’t tossing any blame at the feet of the veteran, and the 38-year-old’s influence will live on with young flamethrower Daniel Bard long after the southpaw’s two months in Boston are a faded memory.

“He got that weird hop over at first and that’s nobody’s fault,” Bard said. “Then he got a ground ball, and that changes the whole perspective. He threw the ball well and deserved better than that.

“I learned a lot from him. I realized that even after 14 years in the big leagues, for him the butterflies really never go away. He said during that ninth inning when you’re closing it out and only three outs away, there’s no slowing it down. There are very few guys that can do that. Maybe Rivera, but that’s about it. Most closers are high-energy guys, and it’s a pretty fast-paced inning, and that’s what I want to do someday no matter where it might be.”

While the numbers are difficult to argue, things might have been different had Youkilis come up with Abreu’s grounder cleanly and the momentum had never been pushed to its tipping point. Or perhaps if the ball had caromed off the Fenway wall and right back to the bearded first baseman — instead of bounding helplessly into the photographer’s pit for the extra-base hit.

Then maybe things might have been different for the rest of Wagner’s eighth-inning efforts, and Papelbon could have kicked off his outing with a clean beginning in the ninth.

Instead, Abreu padded a .300 lifetime batting average against Wagner with his cue shot ground-rule double, and once again a painful loss helped hammer home a lesson that the hurler should have known all along.

Pitchers should never give big league hitters — teammates or opponents — the keys to their kingdom, or they risk having days just like Sunday afternoon when it comes back to haunt them.