Put Terry Collins in the camp of those who believe Jason Bay's paltry showing at the plate is concussion-related.

Bay, who starts a second straight game Wednesday night, enters the series finale against Washington hitting only .158 with seven homers and 18 RBIs in 198 plate appearances.

"I just think that those concussions take an effect on guys," Collins said. "There are times when you see everything you thought that he could bring to the table -- great defender, a good thrower, power, a tremendous teammate. And then, all of a sudden, there will be some times where he struggles. He has no answers to it. This time in his career, we know it's still there. Hopefully with the winter recovery, maybe you'll get something next spring that will really come forward."

Bay has suffered a pair of concussions in the past three seasons that have led to prolonged absences. He crashed into the wall at Dodger Stadium on July 23, 2010 and did not return after that series for the remainder of that season. This season, he suffered a June 15 concussion on what became an inside-the-park homer for Cincinnati's Jay Bruce.

Scouts also have speculated that residual concussion effects have slowed Bay's reaction time at the plate. One NL scout noted Tuesday that Minnesota's Justin Morneau also has not looked the same since suffering a concussion on July 7, 2010.

Bay is signed for next season at $16 million. He also will be owed a $3 million buyout on a 2014 option that would only vest if he logs 600 plate appearances next season.