

| Safeco Field | 1999-2012 | 2013 |
| LF Line | 331' | 331' |
| Left Center | 390' | 378' |
| Deepest Point | 409' | 405' |
| Straightaway Center | 405' | 401' |
| Right Center | 385' | 381' |
| RF Line | 326' | 326' |
The construction crews were busy during the past off-season as the Mariners moved portions of the outfield wall at Safeco Field for the 2013 season. By moving the walls in, the hitters should benefit. This is the first time the field dimensions have changed since the ballpark opened in 1999.
After several months of deliberation and analysis, input from former players as well as from current and past front office personnel and coaches, the decision was made to make the adjustments last fall.
Executive Vice President and General Manager Jack Zduriencik said, "Our goal is to create an environment that is fair for both hitters and pitchers. Considering the current field dimensions as well as the climate in and around Safeco Field, we feel this has been accomplished with the new layout."
From the left field corner to a point about midway between the bullpens, the wall was moved in four feet. The biggest change is from the left field power alley area to straightaway center, where the wall is as much as 17 feet closer to home plate. From straightaway center to right center, the wall was moved in four feet.
Another noticeable change is in the left field corner. The hand-operated scoreboard is longer be in play, and is relocated to the facing of Edgar's Home Run Porch, a new space for fans to gather and watch the game. The outfield wall is now eight-feet high from foul pole to foul pole.
Based on the analysis, it is expected that the number of total home runs hit at Safeco Field will rank in the middle of the pack of the 30 MLB teams in 2013, compared to ranking 27th over the past three seasons.