"I can tell you there are a lot of conversations that go on with him," Farrell said before Sunday's game. "There are some situations that have been overlooked. There is aggressiveness on his part which is a positive, but there are some game situations that need to be addressed and will continue to be addressed. Whether he's run through a stop sign or there have been some things that have taken place on the basepaths that have to be corrected, there has to be better attention to detail paid on his part."
Sierra, 23, was thrown out at the plate on Saturday. Farrell said baserunning has been an issue for the outfielder, who made his Major League debut on July 31.
"There has to be greater attention to the game situation at hand," Farrell said. "The days of laughing about something when something is not done right are over. He's in the big leagues. There are certain expectations. These aren't things that are geared toward talent. They are about understanding the game situation in the proper way."