OAKLAND -- The A's were active at last year's non-waiver Trade Deadline, dealing Ben Zobrist and Scott Kazmir in separate deals for prospects, and they could very well pursue a similar strategy in the coming days. And if this season has shown anything, those types of future pieces can quickly become fixtures of the present. 
Amid injuries and ineffectiveness to others, Sean Manaea, Oakland's top preseason prospect, found a spot in the rotation by the end of April, and after being called up on July 15, Ryon Healy is the team's starting third baseman following a strong 2016 SiriusXM All-Star Futures Game showing. Righty Daniel Mengden enjoyed a promising start to his career before a recent slide led to a demotion Monday, and lefty Dillon Overton makes another spot start Saturday against the Indians.
• A's Top 30 Prospects list
The A's farm system has taken on a different look at the midseason point. Manaea has graduated from MLBPipeline.com's Top 100 Prospects list, leaving behind shortstop Franklin Barreto (No. 55) and first-round Draft pick A.J. Puk (No. 80) as the team's two representatives.
The ranking of baseball's top prospects is done by MLBPipeline.com Draft and prospect experts Jonathan Mayo, Jim Callis and Mike Rosenbaum, who compile input from industry sources, including scouts and scouting directors. It is based on analysis of players' skill sets, upsides, proximity to the Majors and potential immediate impact to their teams. Only players with rookie status are eligible for the list. The rankings follow the Collective Bargaining Agreement guidelines for which players fall under the international pool money rules: Players who were at least 23 years old when they signed and played in leagues deemed to be professional (Japan, Korea, Taiwan, Cuba) are not eligible.
Barreto, 20, is still seen as Oakland's top prospect, despite falling 32 spots from his No. 23 preseason ranking. He's hitting .269/.332/.408 with eight homers and 23 steals in his first full year at Double-A Midland, a slight decrease in power numbers from previous seasons.
Puk, a 6-foot-7 lefty with a mid-90s fastball, was taken sixth overall in this year's Draft, immediately becoming the team's best pitching prospect following Manaea's departure from the list. The 21-year-old is just beginning his career at Class A Vermont, throwing 5 2/3 innings in three starts since making his debut two weeks ago.

The A's Top 30 Prospect rankings have also seen movement.
Healy, 24, is the team's fifth-best prospect, a rise of 13 spots, and he could find himself a graduate of the list by season's end. He's hit .255 with two homers in 13 games, including a walk-off homer Saturday against the Rays, leaving Oakland's manager Bob Melvin to say Healy "isn't afraid of anything."

Cuban outfielder Lazaro Armenteros, MLB.com's fifth-best international prospect and an athletically gifted player, joins the list for the first time at No. 10 following his July 1 signing, as do Draft picks Logan Shore (No. 12) and Daulton Jeffries (No. 15).

Several A's prospects have slid considerably since the preseason, headlined by Matt Olson, who dropped 11 spots to No. 14 overall. The first-base/outfield prospect is hitting .229/.332/.425 with 12 homers at Triple-A Nashville this year, striking out nearly 26 percent of the time.
Casey Meisner, Joe Wendle, Rangel Ravelo and Raúl Alcántara each fell double digits as well.