That the Twins would add Miguel Sano, Alex Meyer and Eddie Rosario to their 40-man roster Thursday, the deadline for shielding eligible prospects from next month's Rule 5 draft, was never in doubt. But Class AA lefthander Jason Wheeler, an eighth-round pick in 2011, was a surprise addition to the list.

But not, General Manager Terry Ryan said, if you watched Wheeler pitch during the season's final month.

"He's been getting better every year, and he really was impressive at the end of the year," Ryan said of the 24-year-old Californian, who posted a 1.42 ERA over his final six starts for New Britain. "He's got impressive size, good mix of pitches, and a mentality that you really like out of a pitcher. … He's on a major league track now."

So are Sano, Meyer and Rosario, the three best prospects in the upper reaches of the Twins farm system. While only Meyer figures to compete for a major league job immediately, it's entirely possible all three will reach Target Field in 2015.

"Whether [Meyer] can take that final leap will be up to him. He's capable — he's shown flashes of being a dominant starter," Ryan said. "We've got high hopes for him."

For Sano and Rosario, too, though both are overcoming difficult seasons. Sano, 21, who has 90 home runs in his minor league career, is one of the best power-hitting prospects in minor league baseball, but the Dominican third baseman missed the 2014 season after elbow surgery in March. And Rosario, 23, is a talented lefthanded hitter who recently batted .330 in the Arizona Fall League, but he spent April and May serving a drug suspension that largely spoiled his season.

"He had some things to prove, some fences to mend, but it did come together this fall," Ryan said of the Puerto Rican outfielder.

Stopping with those four players meant exposing about a dozen other prospects to the Dec. 8 draft, in which any team can pluck veteran minor-leaguers from the system of another team. Players with five seasons of minor league experience, or four seasons if they were signed after turning 19, are eligible if they are not on a 40-man roster.

For the Twins, that means players such as infielder Levi Michael, their first-round pick in the 2011 draft, and Sean Gilmartin, a lefthander and former first-rounder acquired from Atlanta in a trade for Ryan Doumit, can be drafted. Jason Adam, acquired from the Royals in a trade for Josh Willingham, is eligible, too. But players selected in the Rule 5 draft must remain in the major leagues all season or be offered back to their original organization.

"There were a lot of guys we gave a good deal of consideration to," Ryan said. "We felt like we put the four guys on our roster who warranted going on it."