*Jackson, at age 20, remains a premier prospect who merely stumbled a year ago through his first full professional season.
*The Mariners’ system is painfully thin in projectable major-league talent.
Both are probably at least partially true. Nobody is ready to declare Jackson a bust; he was generally viewed in 2014 as the draft’s top high school player.
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"The tool set that made Jackson a prep sensation remains intact," Baseball America reported, "and it may very well be a matter of him putting the pieces together with a fresh start in 2016.
"Jackson combines tremendous bat speed and hand-eye coordination with strength to produce a thunderous swing."
Baseball America ranked right-hander Edwin Diaz as the system’s No. 2 prospect, up from No. 6 before last season, after he went a combined 7-10 with a 3.82 ERA in 27 starts at Hi-A Bakersfield and Double-A Jackson.
The rest of the Top 10: shortstop Drew Jackson, outfielder Tyler O’Neill, pitchers Nick Neidert and Luiz Gohara, outfielder Braden Bishop, pitcher Andrew Moore, outfielder Boog Powell and first baseman/third baseman D.J. Peterson.
Gohara was seventh in last year’s rankings, while Peterson dropped all the way from No. 2 to No. 10 after a disastrous season.
Only two players from last year’s top 10 spent significant time in the majors: shortstop Ketel Marte (No. 3) and reliever Carson Smith (No. 10), but it was the struggles by Jackson and Peterson that prompted new general manager Jerry Dipoto to overhaul the organization’s player-development staff.
Jackson flopped at Lo-A Clinton — batting .157 in 28 games with a .240 on-base percentage and a .213 slugging percentage. That prompted a demotion to extended spring training and a subsequent reassignment to Short-A Everett.
He was better (but not great) at Everett: a .239/.365/.466 slash in 48 games.
So what now?
"He has middle-of-the-order potential," Baseball America reported, "but needs to show he can make the adjustments to reach it and help turn around the Mariners system."
Peterson, 24, is at a crossroads. He was the club’s top pick in 2013 and flashed his potential in 2014 at Hi-A High Desert and Jackson by batting .297 with 31 homers and 111 RBIs in 123 games.
But he turtled last season, spent primarily at Jackson, in batting just .223 with seven homers and 44 RBIs. He is likely to start the season at Triple-A Tacoma.
"Some scouts still believe in his swing," Baseball America cautioned, "but others don’t think he will hit enough to be a regular."
As for the others, O’Neill flashed the sort of breakthrough year in 2015 that Peterson had a year earlier. His challenge will be ti build on it — and not suffer the regression that derailed Peterson and so many others in recent years.
Drew Jackson was a fifth-round pick last June who proved a sensation in batting .358 at Everett with a .432 on-base percentage. Neidert, Bishop and Moore were others from that draft class who had encouraging pro debuts.
The Mariners acquired Powell from Tampa Bay as part of a Nov. 5 trade that also netted pitcher Nathan Karns. Powell, 23, batted a combined .295 with a .385 OBP last season at Double-A Montgomery and Triple-A Durham.
New Mariners center fielder Leonys Martin flashed a little fire Thursday night in the Dominican Winter League playoffs when he was ejected in the ninth inning of Licey’s 6-4 loss to Escogido for arguing a called third strike.
Licey had one out and nobody on base when Martin was ejected.
The Mariners acquired Martin, 27, from Texas in a Nov. 16 trade, and he projects as the club’s starting center fielder. He recently avoided arbitration by agreeing to a one-year deal for $4.15 million.
Martin returned to action Friday and went 1-for-3 with a sacrifice fly in Licey’s 3-2 loss to Escogido, which has a 3-0 lead in the best-of-nine championship series. Martin is batting .250 with a .373 on-base percentage in 20 games for Licey.
REPORT: SANCHEZ SIGNED
Veteran first baseman Gaby Sanchez, who spent last season in Japan, is the Mariners’ latest minor-league acquisition, according to a twitter report by ESPN’s Jerry Crasnick.
The Mariners have not confirmed the signing, but the agreement is expected to include an invitation to big-league camp. Sanchez is likely to battle Jesus Montero for duty as a right-handed complement to lefty-hitting first baseman Adam Lind.
Sanchez, 32, was an All-Star in 2011 at Florida and spent parts of seven big-league seasons with the Marlins and Pittsburgh from 2008-14. He had a .254 average in 700 games with 61 homers and 266 RBIs.
The Mariners selected Sanchez in the 15th round of the 2002 draft when he was a high school senior, but he opted to attend the University of Miami. The Marlins chose him in the fourth round of the 2005 draft.
Sanchez batted just .229 with the Pirates over 123 games in 2014 with seven homers and 33 RBIs before signing with Rakuten in Japan’s Pacific League. He batted .226 in 66 games for Rakuten with seven homers and 18 RBIs.
Bob Dutton: @TNT_Mariners