Tom McNamara, the Mariners amateur scouting director, said he saw Miller and Festa pitch against each other in a game in Butler, Pa., last month.
"If you'd told me before the season that we'd end up taking two D-2 pitchers from Pennsylvania in the first seven rounds, I'd have probably bet against that," McNamara said with a laugh. "But those are two kids that can really throw. It just worked out."
The Mariners also went the small-school route in the first round on Thursday when they landed Mercer University outfielder Kyle Lewis with their first-round pick. Their lone prep pick so far is third baseman Joe Rizzo out of Virginia in the second round.
Seven of the club's first 10 picks were positon players, which is another surprise to McNamara.
"Going in I thought we'd go pitching heavy in this Draft, but when you have good position players right in front of you, you take the best player," he said. "We think we got some good ones."
Track every Mariners pick from Day 2 of the 2016 MLB Draft, which consisted of Rounds 3-10.
The Draft concludes on Saturday, with exclusive coverage of Rounds 11-40 beginning on MLB.com at 9 a.m. PT.
Here's a complete roundup of Friday's selections:
Round 3 (87th overall), Bryson Brigman, SS, University of San Diego
The Mariners continued stocking up on position prospects, landing a 20-year-old middle infielder who missed part of the early season this year with a sports hernia, but returned to hit .372 with 31 runs, 22 RBIs and 17 stolen bases in 47 games in his just-completed sophomore season and was named to the All-West Coast Conference first team for a second straight year.
Brigman, who was also a standout youth hockey player growing up in San Jose, is the only player to have appeared on three world championship teams for USA Baseball, playing on the 16-and-under title team in 2011 and helping win back-to-back titles with the 18-and-under team in 2012 and '13.
Brigman played some second base for Team USA and could be an option at that position as well. The 5-foot-11, 170-pounder was selected in the 40th round of the 2014 MLB Draft by the A's out of Valley Christian High School in San Jose, but he elected to go to the University of San Diego.
Round 4 (117th overall), Thomas Burrows, LHP, University of Alabama
The left-hander was the first pitcher selected by Seattle and some scouts feel the 21-year-old could be a fairly advanced prospect as a hard-throwing bullpen candidate.
Burrows is Alabama's all-time career saves leader with 30 in three seasons. He was 2-1 with a 0.95 ERA and 12 saves with 41 strikeouts and nine walks in 28 1/3 innings over 21 appearances this year as a junior despite missing most of March with an oblique injury.
A finance major at Alabama, the 6-foot-1, 225-pounder has a fastball that tops out around 95 mph and has shown improvement with his slider this season. Burrows attended Mars Hill Bible School in Florence, Ala., where he was the 3A state pitcher of the year as a senior and set school records for home runs and RBIs as a first baseman when he wasn't pitching.
Round 5 (147th overall), Donovan Walton, SS, Oklahoma State
The switch-hitting college senior hit .350 with 44 runs, 14 doubles, a triple, three homers, 43 RBIs and 13 stolen bases in 59 games this past season and became the first player in school history to be a three-time All-Big 12 first-team selection.
The 5-foot-10, 175-pounder from Tulsa, Okla., has been drafted twice before -- in the 36th round in 2012 by the Mets and in the 23rd round in 2015 by the Brewers -- but he stayed in school and is playing for Oklahoma State on Saturday in the Columbia Super Regional against South Carolina.
Walton is a sports management major and academic All-Big-12 selection as well. His father, Robert, played three seasons in the Orioles' Minor League system and is now Oklahoma State's pitching coach. His brother, Davis, was an offensive tackle at Tulsa from 2012-14.
Round 6 (177th overall), Brandon Miller, RHP, Millersville University (Pa.)
The 6-foot-4 junior was 12-2 with a 1.42 ERA and fits the Mariners' strike-throwing profile with 115 strikeouts and 13 walks in 107 2/3 innings over 15 starts this season at the Division II school. Miller was named All-Atlantic Region Pitcher of the Year and is majoring in applied engineering and technology.
Round 7 (207th overall), Matt Festa, RHP, East Stroudsburg (Pa.) University
The Mariners continued unearthing small-school prospects with Festa, a 6-foot-1 senior out of Staten Island, N.Y., who went 11-2 with a 2.35 ERA with 105 strikeouts and 21 walks in 88 innings over 13 starts this year. Like Miller, he is one of 10 finalists for the Brett Tomko Award for the nation's top Division II pitcher. Festa transferred to East Stroudsburg from Dominican College in Orangeburg, N.Y., following the 2013 season and is majoring in business management.
Round 8 (237th overall), Nick Zammarelli, INF, Elon (N.C.) University
The 21-year-old junior is listed as a utility player by the Mariners after playing mostly second and third base for Elon, where he hit .342 with 56 runs, 24 doubles, two triples, nine home runs, 51 RBIs and 10 stolen bases in 54 games this season. The native of Lincoln, R.I., was a Cape Cod League All-Star last summer and a third-team Louisville Slugger All-America selection as a second baseman for Elon this year. Zammarelli was a 28th-round Draft pick by the Red Sox in 2013. His father, Nick, played baseball at College of the Holy Cross.
Round 9 (267th overall), Jason Goldstein, C, University of Illinois
Goldstein was drafted by the Dodgers in the 17th round last year, but he returned for his senior season and led the Illini with a .312 batting average, .402 on-base percentage and 29 RBIs. The 22-year-old was a three-time Academic All-Big Ten selection as an industrial engineer major. His brother, Taylor, pitched for Johns Hopkins University and his dad, Scott, played football at Grinnell College.
Round 10 (297th overall), David Greer, 3B, Arizona State
The 20-year-old has been an outstanding hitter for the Sun Devils, though his position remains a bit uncertain. Greer hit .344 with 49 runs, 23 doubles, two triples, eight homers and 43 RBIs and was an All-Pac-12 first-team selection this year as a junior. The 6-foot-1, 205-pounder played first base, second base, third base and left field this season for ASU and even made his college pitching debut in three games, allowing two runs in 2 1/3 innings.