Paniagua had two brief stints in the majors with the Montreal Expos in 1996-97, but neither were impressive enough for the team to protect him in the expansion draft. The Tampa Bay Devil Rays selected the Dominican righty in November 1997, but dropped him in March 1998 when he seemed apathetic and lazy on the mound during spring training.
The Seattle Mariners, still looking for a righty arm out of the bullpen, picked up Paniagua on waivers, and promoted him to the big-league club at the end of 1998. After recording a 2.05 ERA over 22 innings, Paniagua was a lock for the relief corps the following year. But his master pitches, the forkball and split-fingered fastball, failed him in 1999, and the righty totaled 11 losses from the bullpen before a pulled groin muscle ended his season.
Paniagua bounced back with a fine 2000, sporting a 3-0 record and 3.47 ERA, establishing himself in the Mariners’ bullpen as a reliable right-handed set-up man for Kazuhiro Sasaki.