This is one outlet's own report from Yahoo Sports — the article as it was filed.
Aroldis Chapman Reveals Reason For Red Sox Extension When He Could Have Cashed In As Free Agent

Boston Red Sox pitcher Aroldis Chapman
Last season, the Boston Red Sox agreed to an extension with Aroldis Chapman, keeping him off the open market.
Chapman's deal paid him $13 million for this season and had a conditional mutual option for next season. He is 1/3 of an inning away from reaching the 40-inning threshold for his contract to be guaranteed next year. He will also have to pass a physical. He will make another $13 million next season in Boston.
