Los Angeles Angels pitcher Tyler Skaggs, 27, has been found dead in his hotel room just hours before he was set to play against the Texas Rangers.
Monday's game was postponed due to his death.
A statement on the Angels' website read: "It is with great sorrow that we report Tyler Skaggs passed away earlier today in Texas.
"Tyler has [been], and always will be, an important part of the Angels Family. Our thoughts and prayers are with his wife Carli and his entire family during this devastating time.
"There are no other details at this time, please keep Tyler's family in your thoughts and prayers."
A photo of the Angels team wearing cowboy hats was posted on Skaggs' Instagram account on Sunday, with the caption "Howdy y'all #TexasRoadtrip".
In a statement on their team feed, a Rangers spokesman said: "The Texas Rangers organisation wants to express its deepest sympathies to the family of Tyler Skaggs and to the entire Angels organisation on this shocking loss.
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"The thoughts and prayers of every member of the Texas Rangers and all of their fans are with the Angels organisation at this difficult time."
A statement issued by Major League Baseball (MLB) commissioner Rob Manfred read: "I am deeply saddened by today's tragedy in Texas. All of us at Major League Baseball extend our deepest condolences to Tyler's wife Carli, their family, their friends and all of his Angels team-mates and colleagues.
"We will support the Angels organisation through this most difficult period, and we will make a variety of resources available to Tyler's team-mates and other members of the baseball family."
Fellow Angels pitcher Parker Bridwell tweeted: "I can't believe this, my heart and prayers go out to his wife and family! We lost an amazing human being. Rest In Peace brother."
Angels centre fielder Mike Trout said on Twitter: "Words cannot express the deep sadness we feel right now. OurRead More – Source