New York Yankees right-hander Michael Pineda was ejected in his side's 5-1 defeat to arch-rivals the Boston Red Sox last night after pitching with pine tar on his neck.
Pineda was sent from the game in the second inning after Red Sox manager John Farrell alerted the home base umpire.
Pineda admitted after the match that he had used the tar to help him grip the ball in cold conditions at Fenway Park, which is against MLB rules which state a "pitcher shall not apply a foreign substance of any kind to the ball".
The 25-year-old Dominican, who had been accused of the exact same indiscretion against the Red Sox on 10 April, is now set to face a suspension.
Pineda's opposing pitcher John Lackey led the Red Sox to a much-needed win as he threw eight innings, allowing one run, no walks and 11 strikeouts.
The Milwaukee Brewers improved their league-best record to 16-6 on the back of a 5-2 win at home to the San Diego Padres.
Jean Segura ended his long wait for a home run with a three-run shot in the second inning.
The Los Angeles Dodgers remained a game clear at the top of the National League West with a 5-2 win over the Philadelphia Phillies.
Closest divisional rivals the San Francisco Giants won a wild 12-10 game against the Colorado Rockies after 11 innings.
Hector Sanchez put the Giants ahead in the eighth inning with a solo homer before icing the contest with a grand slam in the 11th.
The Chicago White Sox also won on the back of a clean-out hit, as rookie Marcus Semien cleared the Comerica Park fence with bases loaded in the seventh inning of a 6-4 success over the Detroit Tigers.
The Atlanta Braves are sitting pretty at the top of the National League East after beating the Miami Marlins 3-1, while the Washington Nationals edged the Los Angeles Angels 5-4.
The Minnesota Twins needed 12 innings to see off the Tampa Bay Rays 6-4 while the Baltimore Orioles won 10-8 at the Toronto Blue Jays.
The Seattle Mariners snapped an eight-game losing streak, 5-3 over the Houston Astros, on the back of third baseman Kyle Seager's two homers.
The Arizona Diamondbacks were 7-5 winners at the Chicago Cubs while the Cincinnati Reds also won on the road, beating the Pittsburgh Pirates 5-2.
Martin Perez fired his second straight shut-out as the Texas Rangers beat the Oakland Athletics 3-0.
The Cleveland Indians topped the Kansas City Royals 5-3 while the New York Mets got back to winnings ways 3-2 over the St Louis Cardinals.