Mariners general manager Jack Zduriencik told "The Kevin Calabro Show" Tuesday that the club decided to alter the dimensions after soliciting the input of former players as well as current and past coaches and members of the front office.
"What we wanted to do was create a fair ballpark and to eliminate extremes, and that was our goal," Zduriencik said. "Those of us that have watched how this field plays [have noticed] that there are extremes, and we wanted to kind of neutralize that and just make it a fair ballpark."
The biggest change will be in the left-field power alley, where the distance from home plate will decrease from 390 feet to 378 feet. Straightaway center field will move in four feet, decreasing the distance from 405 to 401. From straightaway center to the right-field power alley, the wall will move in four feet, decreasing the distance in the right-field power alley from 385 to 381.
The distance down the left-field foul line will remain 331 feet, but the hand-operated scoreboard will be relocated so that it's no longer in play. The wall in the left-field corner, currently 16 feet high at the top of the scoreboard, will be reduced to eight feet, making the outfield wall the same height from foul pole to foul pole.
The dimensions will remain the same from the right-field power alley to the right field line.
The possibility of shortening the dimensions at Safeco Field has been a topic of debate in recent seasons, especially as the Mariners' offense has struggled at a historic rate. Seattle is on pace to finish last in the American League in runs scored for the fourth consecutive season.
Zduriencik agreed that the spacious dimensions combined with the cool air coming off the Puget Sound got into hitters' heads.
"I don't think there's any doubt about it and I think a lot of the discussions we had with guys that played here in the past said the same thing. You come out of spring training and you roll in here for the first two, possibly three months [and] the air's heavy, it's damp, the ball doesn't move, the ball doesn't fly. It makes it an extreme ballpark to drive the baseball in," he said.
"So what we wanted to do was just alter the dimensions somewhat where it would play fairly, and we think we've accomplished that."
The changes to the dimensions are the first since Safeco Field opened in 1999.