"Chris will give us another tool in our bag as we take the information we receive from our video advance scouting group and apply it to our day-to-day needs on the field," McClendon said.
Prieto will travel with the Major League team all season, but will not be permitted to be in uniform during the game.
Prieto is in his second season in the Mariners system and was slated to manage Class A Clinton in the Midwest League this season prior to being promoted to the big league staff. He led the Pulaski Mariners to the Appalachian League Championship in 2013 with a league-best 41-27 record.
Prior to joining the Mariners, Chris spent two seasons in the San Diego organization as a coach with the Eugene Emeralds.
Chris spent 13 seasons in the minor league systems of the Padres (1993-99), Dodgers (2000-2001), Astros (2002), Athletics (2003), Cardinals (2004) and Angels (2005). He made his Major League debut for the Angels in 2005, appearing in a pair of games.
Prieto is a native of Carmel, CA, and graduated from Carmel High School prior to attending the University of Nevada. He was drafted by the San Diego Padres in 1993.