PHOENIX -- On a two-year church mission to Cuernavaca, Mexico, right-hander Adam Miller became fluent in Spanish but found himself isolated from baseball, his sport of choice.  Since returning to the U.S. in 2011, Miller has become fluent in fastball, first at Brigham Young University and now with the Diamondbacks, who selected him in the 20th round of the 2013 draft. If he does not have the strongest arm in the system, he is very near the top.  Miller has hit 100 mph numerous times the last two years and has topped out at 101 this year while taking over as the closer at Double-A Mobile when Enrique Burgos was promoted to the Diamondbacks several weeks ago.  At 25, Miller is one of the oldest players in the prospect-heavy Southern League, which can be a quick conduit to the majors. But when your fastball is in triple digits, age is not the first number scouts notice.  The D-backs drafted Miller because of that arm strength and first tried him in the starting rotation at short-season Missoula in 2013 and then early at Class A South Bend last season, with some success. They found that Miller's velocity dipped somewhat as the starts piled up, so they considered a move him to the bullpen. When he struck out six of the 10 batters he faced after a quick look in relief in the rookie Arizona League last summer, the D-backs new they had something. Instead of pitching at 92-93 mph, Miller was in the high-90s.  "We drafted him because we knew he had arm strength," D-backs director of player development Mike Bell said. "When we put him in the 'pen, everything fell into place. He took off."  Former major league Doug Bochtler, the pitching coach at Kane County this season, worked with Miller on developing a slider, which Bell said has become a strikeout pitch.  "That was a turning point," Bell said.  Miller is 0-1 with four saves and a 2.13 ERA in 12 appearances at Mobile, beginning the season in a setup role. He has 18 strikeouts against three walks in 12-2/3 innings while giving up nine hits. He is averaging 12.8 strikeouts per nine innings, has an 0.947 WHIP, and has been scored on in only two of his outings. He is working on a streak of eight consecutive scoreless appearances through Wednesday.  The D-backs will not rush Miller, but as an older player, he might be a quick riser.  "It's hard not to like 97, 98, 100, 101," Bell said.  --First baseman Danny Dorn continued his late-inning heroics back in Reno. After hitting a two-run double off Atlanta's Craig Kimbrel in the ninth inning last Saturday, Dorn hit a two-run walkoff homer to beat El Paso, 2-1 in the 10th inning Wednesday. Dorn was 5-for-8 in two games since rejoining the team.  --Left-hander Robbie Ray threw 46 pitches in the first inning Wednesday and was removed from the game. He gave up three hits, walked two and struck out the side in his first outing since last week's quality spot start for the D-backs in Colorado, where he gave up one run on five hits and no walks in six inning.  --Peter O'Brien, whose eight homers are tied for sixth in the minors, has moved around a lot recently. He has caught and played first base, left field and DH in the last week.  --Jarrod Saltalmacchia is expected to join Reno this weekend, when the Aces have a string of eight games in which they use the DH.  --First baseman Rudy Flores, who saw action in several spring training games with the D-backs, was seventh in the league with 22 RBI. A free-swinger with power, he had six doubles, four homers and 36 strikeouts in 118 at-bats.  --Right-hander Brandon Sinnery, another non-drafted free agent signed by scout Chris Carminucci, retired 18 of 20 in one stretch to improve to 4-1 in a victory over Mississippi on Tuesday. A co-captain and MVP at the University of Michigan in 2012, Sinnery has given up one earned run in five of his six starts and is tied for second in the league in victories.  --Right-hander Yoan Lopez, who missed his last turn through the rotation because of a blister, is 10th in the league with a 2.22 ERA.  --Right-hander Zack Godley, 6-0 with a 1.32 ERA, is tied for the minor-league lead in victories and leads the Cal League in both victories and ERA. Godley, 6-foot-3 and 219, has given up 39 base runners in 59 innings.  --Pitching coach Gilbert Heredia's staff leads the league with a 2.55 ERA, almost a run lower than the second-best team in what is known as a hitter-friendly league. They have a league-high six shutouts and a 1.08 WHIP, also the best marks in the league.  --The Rawhide had a seven-game lead in the Cal League North and were 24-9, the third best record in the minors.  --Left-hander Zac Curtis, a sixth-round pick last year out of Middle Tennessee State, had not given up a run in eight of his last 10 outings and had converted all four save opportunities. Not overpowering, Curtis nevertheless had 19 strikeouts and three walks in 13 innings while limiting opponents to a .163 batting average.  --Right-hander setup man Cody Geyer, a 14th-round pick in 2011 who missed most of the 2012 season after undergoing Tommy John surgery, had a 1.08 ERA through 13 appearances. It is his first year on a full-season team after playing with short-season Missoula and Hillsboro the last two years.  Follow Jack Magruder on Twitter  VIDEO: 10th Inning Cup of Coffee makes its 2015 debut on Sunday, May 17, immediately following the Diamondbacks-Phillies game. Tony La Russa joins Steve Berthiaume for a wide-ranging discussion of his baseball career.
D-backs minor-leaguer Adam Miller got a late start on his pro baseball career, but he's coming on fast while showing a 100-mph fastball as Mobile's newly installed closer.