Why wasn't John Lackey ejected for plunking Matt Joyce?

It's always interesting how umpires handle the assorted bean ball wars that break out from time to time in Major League Baseball.

On several occasions, I've seen pitchers unfairly tossed for hitting a batter. Other times, a pitcher plunks a guy intentionally and somehow gets away with it.

Such was the case in Monday's game between the Boston Red Sox and the Tampa Bay Rays. The Red Sox won 10-8 in 14 innings, but the contest was marred by a bench-clearing scrum in the sixth inning.

The principle combatants were Red Sox right-hander John Lackey (pictured) and Rays outfielder Matt Joyce.

Joyce homered off Lackey in the first inning. In a later at-bat, he lined a 3-0 pitch deep and foul into the right-field stands. After hitting the foul ball, Joyce dropped his bat and appeared to admire the blast as it landed harmlessly in foul territory. Lackey took exception to the display. After retiring Joyce, he had some choice words for the Tampa Bay hitter on his way off the field.

In the bottom of the sixth inning, Joyce came to the plate again with two outs and nobody on. If you're ever going to hit somebody, two outs and nobody on is the ideal situation. Lackey took advantage, drilling Joyce in the back, right between the numbers. Anyone with an IQ over 15 knows it was intentional after the events that had taken place earlier in the game. The benches emptied. Order was eventually restored, yet for some reason Lackey was allowed to stay in the game.

I've seen pitchers get ejected for far, far less than that. If you were umpiring this game, how could you not know that inside pitch was intentional?

Now, to be fair, you can make a good case Joyce had it coming to him. It's dumb to stand in the batters box and admire a long foul ball. In addition, Lackey faced only one more batter after the plunking, so his being allowed to stay in the game had zero impact on the outcome of the game.

That said, if umpires are supposed to eject pitchers for intentionally throwing at hitters, Lackey should have been tossed. The enforcement of these rules seem to vary from umpiring crew to umpiring crew, and that shouldn't be. There's gotta be a better way to handle these situations, right?