To most, it was fairly obvious that Michael Pineda had pine tar on his hands during the first 4 innings of his last start against the Red Sox. (Though I do think it could have been BBQ sauce.) Pineda denied it, calling it dirt and sweat, but it's hard to believe that it took him 4 innings to wipe it off, especially as the slick surface of mud would likely have an adverse effect on his command. The mysterious glob also moved over to his wrist after the NESN broadcast found the substance. The fact that it remained for so long and moved around to a more concealing area makes the situation awfully suspicious. NESN called Pineda a cheater, however the Red Sox' coaches and players had no problem with whatever Pineda used. It's an accepted practice to break this rule, and the Red Sox' own Clay Buchholz and Jon Lester have repeatedly been accused of using their own gripping agents. While it might seem odd that hitters would have no problem with pitchers gaining an advantage from pine tar, the likely result of not using it is poorer command and more hit by pitches.
I have my own opinions on what the MLB should do with their pine tar rules, but I'd like to focus more on how it affected Pineda's performance, since it's very unlikely we see him using it in future games. After the 4th inning, when Pineda had 60 pitches, the NESN broadcast showed a close up of pine tar. Immediately after, the substance moved from the bottom of his hand to his glove-side wrist.
Immediately after Pineda removed the "pine tar" from the bottom of his hand, his velocity decreased rather significantly. Where he was sitting 93-95 mph from the 1st through 4th innings, he sat around 89-91 mph with his last 34 pitches, topping out at 91.8 mph. The velocity in the last few innings was right where he sat in Spring Training, where we didn't see any use of pine tar. In his first start against the Blue Jays, it looked like Pineda also had something on his hand, and in that start he didn't show the same velocity decline as he hit 93.6 mph and 94.8 mph with his last two fastballs of the night.
Movement-wise, it's much more difficult to see a difference between the first 60 pitches and his last 34 pitches. Perhaps he cuts the fastball more without the "pine tar", but there's less significance here than with what we saw in his velocity.
Pine tar is used to gain a grip on the ball, and it's odd that he'd see such a large velocity decline without the grip advantage. Perhaps Pineda is still working up his strength, or maybe the cooler weather slowed him down. The results don't necessarily point to a huge advantage with the "pine tar", but as we're very unlikely to see Pineda use the substance after NESN publicized it, it'll be interesting to see if he shows an immediate lower velocity in his next start against the Cubs.