Mariners trade one of top prospects, Tyler O'Neill, to Cardinals for pitcher

SEATTLE (AP) — The Seattle Mariners paid a hefty price to add a pitcher who may not be ready to help them in the playoff hunt this season.

The Mariners acquired young left-hander Marco Gonzales from the St. Louis Cardinals on Friday in exchange for top outfield prospect Tyler O'Neill, the second move to add pitching depth in as many days by Seattle. The Mariners acquired veteran reliever David Phelps from Miami on Thursday.

While Seattle will have Gonzales under club control for a number of seasons, he may not be the impact arm to help the Mariners in this year's chase for a wild card spot in the American League. Gonzales has pitched once in the majors this season as he continues to recover from Tommy John surgery that sidelined him for the entire 2016 season.

Seattle is expected to have Gonzales begin at Triple-A Tacoma.

"Marco is a quality athlete with high character and a strong pitching pedigree who we feel fits our roster well in both the near and long term," Seattle general manager Jerry Dipoto said in a statement. "We find his current performance, preparedness and proximity to the major leagues to be very appealing traits in a pitcher, particularly a young lefty who is now under club control through the 2023 season."

Gonzales, 25, has deep ties to the Pacific Northwest as a collegiate star at Gonzaga and makes his offseason home in Seattle. He showed flashes of promise early in his career with the Cardinals, but injuries have derailed most of the past two seasons. He missed parts of the 2015 season due to a pectoral injury and then needed elbow replacement surgery that kept him out all of 2016.

Gonzales was 6-4 with a 2.90 ERA in 11 starts at Triple-A Memphis this season and since June 18 was 5-1. His one start in the majors didn't go well. He gave up five earned runs in 3 1/3 innings in a loss to Milwaukee.

The price Seattle paid for Gonzales was significant. O'Neill was considered one of the top prospects in Seattle's farm system and had been on a tear of late at Triple-A Tacoma with five home runs in the last five games. The 22-year-old O'Neill had 19 home runs in 93 games at Triple-A and two years ago hit 32 home runs in the Single-A California League.

O'Neill played for Team Canada in the World Baseball Classic and was rated among the top five prospects in Seattle's farm system by a number of organizations.

"This was more of a traditional trade in the sense that O'Neill was an outfielder with upside in the Mariners organization and Gonzales was a pitcher with upside in our organization," Cardinals president of baseball operations John Mozeliak said in a statement. "If you look at the depth we have with the pitching in our system, it allowed us to make a move like this to improve. We are excited for Tyler to join our organization."