The Red Sox played Game No. 53 last night. Same with Dustin Pedroia. Given what we now know about what Pedroia has been dealing with since the first game of the season — a complete tear of the ulnar collateral ligament in his left thumb — last night could have been Game No. 2 for Pedroia. For most players, it would have been and should have been No. 2. A torn UCL in the thumb takes about eight weeks to heal. Last night marked the beginning of the ninth week of the season. To Pedroia, the idea of missing April and most of May with an injury he considers nothing more than a flesh wound was repugnant. So was hearing that his previously unknown injury was going to become public knowledge. “People shouldn’t know if you’re 100 percent or not. It is what it is, and it’s my responsibility to perform well,’’ Pedroia said before taking his usual spot at second base against the Phillies. “My mindset is if I’m nicked up, I have to find other ways to perform. That’s the way I think about it. Maybe I’m crazy.’’ Pedroia did not make the best baseball decision of his career in the ninth inning of Opening Day on April 1 at Yankee Stadium, where he slid headfirst into first base in the ninth inning with the Red Sox up by six runs. He jammed his thumb on the bag and the next day had an MRI. It revealed more than a nick. Pedroia said he was told he had a complete tear of the UCL, although it was impossible to say if it was a pre-existing tear or the result of that slide. The soreness and discoloration were real, however. Doctors told Pedroia he could play through the injury if he could withstand the symptoms and that he would not risk doing long-term damage. The first part of the equation was easy for Pedroia. Once he heard the second part, the decision entered no-brainer territory. “Yeah, I’m smarter than a lot of people think I am,’’ Pedroia said. “I understood. You go and come back in eight weeks — that’s a lot of ballgames without one of the team’s best players, so my job’s to go out there and do the best job I can to help the team win. That’s the way I look at things.’’