Saunders had his best offensive year last season at age 29. He hit 24 homers and posted a .815 OPS. If he can come close to those numbers in his age 30 season, he will be a significant upgrade to the Phillies' offense in 2017.
Last year, he was primarily a left fielder (106 games LF; 22 RF) but in 2014 with the Mariners, he played more right (68 RF, 12 CF, 1 LF). In 2012 and 2013, he played mostly CF for the Mariners. He should be fine in either left or right this year with the Phillies, depending on who else is starting in the outfield, and if needed in a pinch, he could handle center.
I think Williams and Quinn need AAA time and as several posters have noted, Altherr probably still is not 100% recovered from the wrist injury. Even with Herrera, Kendirck and Saunders on board, he should still get a good amount of playing time.
If Altherr proves he is ready to be a full time starter and one or more of the outfielders at AAA is burning it up, then Sauders could be a trade chip in July or even in August. If he is having a season close to his last season, he could be a sough commodity. Should he have a strong season and remain with the Phillies all year, he could be a candidate for an off season deal if the Phillies pick up that team option. If the Phillies don't see interest in him and don't see him in their 2018 plans, they can exercise the $1 million buyout and make him a free agent after this season.
Put me in the "like this signing" column.