SCOTTSDALE, Ariz. -- While Spencer Howard emerged as the Phillies' best pitching prospect this summer, he also missed two months with shoulder soreness and totaled just 71 innings between four Minor League stops. So he headed to the Arizona Fall League to get some more work and to continue to refine his impressive repertoire.

Mission accomplished. Howard made his final start of the AFL season Thursday night and looked sharp while throwing three scoreless innings for the Scottsdale Scorpions. The West Division champion Surprise Saguaros feasted on Scottsdale's bullpen as soon as he departed, exploding for 10 runs in the fourth and fifth innings en route to a 10-2 victory.

• Box score | Phillies Arizona Fall League updates

Howard pounded the zone as well as he had all fall, throwing 32 of his 46 pitches for strikes, and topped out at 99 mph with his fastball. He whiffed four of the 10 batters he faced, three of them on heaters, and gave up only a walk. He posted a 2.11 ERA while fanning 27 in 21 1/3 innings and ranking third among AFL starters with a .137 opponent average.

"I feel like I took a few steps forward facing better competition and hopefully, [I can] just build off this continuing into the offseason and go from there," said Howard, a right-hander drafted in the second round out of Cal Poly San Luis Obispo in 2017. "To prove to myself that I can do it after having some sort of discomfort is probably the biggest thing for me mentally."

Howard, 23, arrived in Arizona with a reputation for being able to overpower hitters with his mid-90s fastball and hard slider. In the Fall League, he impressed scouts with one of the best changeups in the developmental circuit. He sells the low-80s offering with fastball arm speed, and it fades and dives as it arrives at the plate.

Though it hadn't attracted a lot of attention in the past, Howard said he has trusted his changeup more than his breaking pitches for a while.

"I've always had probably the most confidence with it amongst my secondary stuff," Howard said. "Maybe people are starting to notice it more of something, but I feel like I've always been most confident with fastball, changeup. Then slider, curveball have been either there or they're not."

Once Howard left, DH Nick Banks (Nationals) opened the scoring with a two-run double in the top of the fourth, beginning a flood of 10 runs in the next two innings. Banks and right fielder Josh Stowers (Yankees) each reached base three times and drove in two runs for the Saguaros.