Sierra had agreed to a six-year, $30 million deal in mid-January. The Dodgers expect his visa issues to be resolved in a few days so he can report to Major League camp.
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"He's got a lot of power in his arsenal, we like his makeup, he's fairly far along, but still has some room to grow as we turn him into a Major League pitcher," said Josh Byrnes, senior vice president of baseball operations.
Byrnes, who saw Sierra earlier this month in Miami, said the pitcher has not thrown any bullpen sessions so he will be behind teammates.
The 24-year-old Sierra, who is listed at 6-foot-1 and 168 pounds, pitched for four seasons in the Cuban League, where he went 16-21 with a 4.23 ERA and a 1.490 WHIP, primarily as a starter.
Byrnes said the club theorizes that the pedestrian stats are a function of a pitching style that leaned more on breaking balls and varying arm slots than Sierra's velocity, which averages 97-98 mph with a four-seam fastball and 91-93 mph with a two-seam fastball.
"We like his secondary pitches, we like his makeup, but the standout is the explosive two-seamer," he said. "There's a lot of positives to build off. He knows that part of his history may be a function of a different style of pitching. Throwing strikes here is essential."
Club officials have mentioned the possibility that Sierra could arrive in Los Angeles as soon as this year as a reliever, but Byrnes said that isn't the current priority.
"If you see him on the right day, you'd say that he will get Major League hitters out in a short stint," he said. "But the long-range is to see if we can make him a starter."
Because of his age and experience, Sierra was not subject to MLB's international signing guidelines and the financial restrictions imposed on clubs like the Dodgers who have spent lavishly on international players in the past year. He left Cuba last April, and he was declared a free agent in December.
In an attempt to play catch-up after being dormant in the international market for years, the Dodgers have been particularly aggressive in the Cuban market since they overwhelmed Yasiel Puig in 2012 with a seven-year, $42 million deal. Puig was an immediate sensation, prompting the club to scoop up infielders Alex Guerrero ($28 million), Erisbel Arruebarrena ($25 million) and Hector Olivera ($62.5 million), with mixed results.
That hasn't stopped them in the past few months from signing Cuban pitcher Yadier Alvarez and fellow Cuban prospects Yusniel Diaz and Omar Estevez.
The hard-throwing Montas, acquired in the offseason from the White Sox, underwent surgery last week to remove an injured rib and is expected to miss anywhere from two to four months.
Montas said he first felt discomfort in his upper back while throwing in the offseason and an MRI revealed a stress reaction.