Whalen, 22, received his first five major league starts previous year, allowing a 18 earned runs and a dozen walks but also limiting opposing batters to twenty base hits while compiling a healthy 25 strikeouts.
After an outstanding first half in 2011, Seattle traded Fister to the Detroit Tigers for four players, the most notable of which was reliever Charlie Furbush, in what was widely regarded one of Jack Zduriencik's worst moves. Upside remains for the powerful right-handed bat, but Atlanta's minor-league staff will be charged with jumpstarting Jackson's development.
Jackson, 20, was the Mariners' No. 1 pick and sixth overall in the 2014 draft.
Former first-round pick Alex Jackson, an outfielder who began the last two seasons as the top-rated prospect in the Mariners' organization, is heading elsewhere. 6 overall pick in the 2014 draft - to the Braves for two right-handed starting pitching prospects.
Though Rob Whalen and Max Povse are relatively young, they could receive invites to Spring Training with an outside shot at making the starting rotation.
The trade also frees up a 40-man roster spot for Atlanta to presumably add super-utility free agent Sean Rodriguez.
With the trade earlier in the week that sent Taijuan Walker to the Diamondbacks, the Mariners were in need of some pitching depth beyond Felix Hernandez, Hisashi Iwakuma, James Paxton, Ariel Miranda and Nathan Karns. Up to that point in the season, Whalen also started 21 games across Double-A and Triple-A for the Braves. His season ended in late August with a trip to the disabled list with shoulder fatigue.
He spent most of the season in the minors at Double-A MS and Triple-A Gwinnett, where he was a combined 7-5 with a 2.49 ERA in 21 starts. He had 94 strikeouts and 37 walks in 101 1/3 innings pitched. He posted a 2.40 ERA, 1.192 WHIP, and 112 strikeouts over 120 innings of work. He made three starts with Gwinnett before joining the Braves. Working past year at the High-A and Double-A levels, he ran up 158 innings of 3.36 ERA pitching with 7.9 K/9 against 1.7 BB/9 - though his strikeout numbers drooped following his promotion. He has a fastball with plenty of sink that sits around 93-94 miles per hour but can touch 96 miles per hour. Ironically, the Mariners acquired Weber, 26, in a November 2 waiver claim from the Braves.