Also added was right-hander Justin Miller, who was signed in September out of the Texas Rangers organization. No players were removed.
The moves bring Detroit's 40-man roster to 39, leaving a spot open in case of a free-agent signing or trade in the next couple weeks. Players can be outrighted off the roster to make room if need be, but Wednesday marked the last day Rule 5-eligible players could be added.
Players first signed at age 18 must be added to 40-man rosters within five seasons or they become eligible to be drafted by other organizations through the Rule 5 process. Players signed at 19 years or older have to be protected within four seasons. Clubs pay $50,000 to select a player in the Major League phase of the Rule 5 Draft, slated to take place on Dec. 12. If that player doesn't stay on the 25-man roster for the full season, he must be offered back to his former team for $25,000.
In other words, an international player or high school draftee signed in 2009, assuming they were 18 or under as of June 5 of that year, must be protected. A college player taken in the 2010 Draft is in the same boat.
Of the players added, Lobstein and Lennerton were the most likely to attract a Draft pick. The Tigers know that well, having traded to acquire Lobstein after the Mets selected him in last year's Rule 5 Draft, and then trading again with Tampa Bay to acquire his full rights in March. The 24-year-old responded with his best season as a pro, posting a 13-7 record and 3.27 ERA in 28 starts between Erie and Toledo.
In a system that has had to rebuild pitching depth in the upper levels, Lobstein looms as a potential insurance starter in Detroit, much like Jose Alvarez became this season.
Lennerton, who turns 28 in February, is near the oldest end of the prospect scale, and any path to the big leagues is blocked in Detroit by Prince Fielder and Victor Martinez. However, his left-handed power hitting was likely to attract interest in a pick after the Tigers had discussed his name in trade talks over the summer. He followed up a 21-homer 2012 season at Erie by batting .278 with 17 homers and 57 RBIs at Toledo. The majority of that damage came in the first half, earning him Futures Game and Triple-A All-Star consideration.
Essentially, Lennerton provides the Tigers insurance in case of an injury to Fielder or Martinez, but he would've left a void of power hitting in the upper levels of the Tigers' system if another team had drafted him.
The Tigers signed Miller in September after the Rangers had released him coming off a season shortened by recovery from 2012 Tommy John surgery. His last full, healthy season was 2011, but he was outstanding, with a 9-1 record, 1.81 ERA and 13 saves at Double-A Frisco.
Miller has pitched just 27 innings over the past two years, but he fit the profile of a high-risk, high-reward pitcher that might have attracted a pick.
Three of the other four players were among the top 11 in MLB.com's midseason Top 20 Tigers prospect rankings. Fields, who will turn 23 in January, ranked third on the list amidst an offensive breakthrough season this past summer, batting .284 at Erie with 27 doubles, 10 home runs, 58 RBIs and 24 stolen bases in 31 attempts. The left-handed batter was the SeaWolves' everyday center fielder and can play all three outfield positions.
A wrist injury scuttled any plans for extra work in the Arizona Fall League or winter ball, but Fields is expected to be ready for Spring Training without any surgery. He'll likely head to Toledo to begin next season.
The 22-year-old Suarez, Detroit's fourth-ranked prospect, spent most of 2013 at Erie, part of it alongside fellow Tigers prospect Hernan Perez. Between 111 games for the SeaWolves and 25 in Lakeland, Suarez batted .264 with 30 doubles, 10 homers and 57 RBIs. He made 36 errors at shortstop between the two stops.
Moya, No. 11 on the Tigers' prospect list, is a big talent at 6-foot-6 and 230 pounds, but the 22-year-old is still working on translating his athleticism into the field. After an encouraging 2012 season at low Class A West Michigan, Moya batted .255 with 12 home runs and 55 RBIs in Lakeland.
Valdez, who turns 24 in March, was the closer on that Lakeland squad by season's end, racking up 33 saves between there and West Michigan in a season that put him on the prospect radar. The right-hander allowed 32 hits over 49 1/3 innings, walked 34 and struck out 67.
A year ago, the Tigers used the roster deadline to make their arbitration moves, releasing Ryan Raburn instead of waiting until the deadline for tendering players a contract. This year, they didn't need the space, which means any non-tenders probably won't happen until the Dec. 2 deadline.