Pressly, who turns 24 on Dec. 15, posted a 2.93 ERA in 27 2/3 innings at Double-A Portland after being converted to a reliever last season. It came after he had a 6.28 ERA at Class A Advanced Salem in 20 games, including 12 starts.
"I think this guy is in transition as starting pitchers sometimes are," Twins director of pro scouting Vern Followell said. "This guy has been a starter for several years. Boston just moved him to the bullpen, and his velocity has spiked a little bit and his curveball is better."
Followell said Pressly possesses a 94-95 mph fastball with a power curveball, and has the potential to pitch in the back end of the bullpen.
Pressly, an 11th-round pick in the 2007 First-Year Player Draft, mostly struggled as a starter before becoming a reliever last year. After impressing at Double-A Portland, he carried it over to the Arizona Fall League, where he had a 3.86 ERA with 18 strikeouts and just one walk in 14 innings.
"This guy definitely has the two pitches to throw late in the game," Followell said. "Obviously, a lot more goes into it than that like throwing strikes, commanding and handling pressure."
Pressly, a 6-foot-3, 175-pounder, must remain on the Twins' 25-man roster for the entire season, or else be offered back to the Red Sox. Another option -- if they don't want to keep him on the active roster all year -- would be to offer him back and acquire him in a trade like the Twins did in 2010 with left-hander Scott Diamond.
The Twins have had success with Rule 5 Draft picks in the past, as it's how they acquired players such as Shane Mack, Johan Santana and Diamond.
"If you look at the numbers, we're not successful most of the time like everybody else, but we've had some good ones along the way," Followell said. "So that's why we keep throwing our hat in there and giving it a shot."
The Twins also selected third baseman Mark Sobolewski, 25, from the Blue Jays organization and lost right-handed pitcher Tom Boleska to the Orioles in the Triple-A phase of the Rule 5 Draft.
Sobolewski is regarded as an above-average defender at third and hit .249 with 21 homers, 20 doubles and 59 RBIs in 117 games between Double-A New Hampshire and Triple-A Las Vegas.
"This is a guy we've seen for a long time," Followell said. "I saw him in high school in a big matchup. He hit for power at New Hampshire. He's always been a good player. He was a shortstop way back when and his power has kind of spiked."