The 27-year-old was hurt on the fifth pitch of his spring training debut Tuesday at Port St. Lucie, on a one-hopper off the bat of the New York Mets' Francisco Lindor for the second out of the first inning. The ball hit the finger as Valdez grabbed the ball, and after throwing to first for the out, he flexed the finger several times.
He took a few warm-ups and stayed in the game. Valdez finished two innings, throwing 24 pitches.
"Following his outing, we decided to have Framber examined," Astros general manager James Click said Wednesday. "The X-ray revealed the injury. At this point, the medical staff needs to do additional tests and imaging before deciding on the next steps. We will know more in the upcoming days."
Valdez was 5-3 with a 3.57 ERA in 10 starts and one relief appearance last year, striking out 76 and walking 16 in a team-high 70⅔ innings.
Houston already was missing ace Justin Verlander, who probably will miss the entire season after Tommy John surgery on Sept. 30. Valdez had been projected to be part of a rotation that includes Zack Greinke, Cristian Javier, Lance McCullers Jr. and Jose Urquidy.