Perhaps there’s now an explanation for Wei-Yin Chen’s late-season struggles. After a winless final seven decisions Chen underwent surgery on his right knee to remove small bone spurs the Orioles announced on Thursday night. Chen’s surgery will be much bigger news in his native Taiwan. Here it was buried under the Manny Machado surgery avalanche. He missed two months with a strained oblique and won his first three decisions after his July return. Then the left-hander won just once in his last 11 starts finishing with a 7-7 record and 4.07 ERA. Chen has had a hard time in the latter part of his first two seasons. The surgery which was performed by Dr. Richard Steadman in Vail Colorado took place last week.