The Red Sox made two errors in their 4-2 victory in Game 4, including one on a routine ground ball single to Jacoby Ellsbury that allowed the Cardinals to take an extra base that led to a run.
"There's been self-induced errors, there has been outfield grass where the ball jumps up on a guy, there's been some miscues," Farrell said. "You can't point to youth being a reason, because it's been spread across the board. You've got two teams that are going at it to their maximum abilities."
Farrell thinks that the Ellsbury error was a fluky one.
"They just replaced the grass here six weeks ago after a football game. And it's fast, it's not true," Farrell said. "And the ball jumped up last night on one of those seams, on the turf."
The Sox also made two errors in their loss in Game 3, including one by Ellsbury and the obstruction call by Will Middlebrooks that lost the game. For all the talk about obstruction on Middlebrooks, catcher Jarrod Saltalamacchia didn't make a good throw on that play.
"I wish I could tell you it's just like a June game, but it's not," Farrell said. "I can't say it's mental fatigue. I mean, how can you not be up in this environment? I think two teams realize that we're very comparable in outcomes, abilities, all that. It's just two teams getting after it."
The pivotal play that led to the Game 2 loss by the Red Sox featured two errors on one play -- by Saltalamacchia and pitcher Craig Breslow.
There was just one error in Game 1, an easy 8-1 win for the Sox.
Ian Browne is a reporter for MLB.com. Read his blog, Brownie Points, and follow him on Twitter @IanMBrowne. This story was not subject to the approval of Major League Baseball or its clubs.