The defending champion experienced spasms in his left arm during a 15-minute practice session Saturday afternoon and was advised to withdraw by tournament physician Dr. David Dines. Haas suffered the injury by overcompensating for shoulder tendinitis.
"At the beginning of the week, I didn't know if I would be able to play, but it shows how much I like to compete," Haas said. "I'm icing it, having ultrasound and taking anti-inflammatories, but it's still a little swollen. I'm doing everything to get better, so hopefully it will be right for next week."
Srichaphan advanced to his second straight ATP final after reaching the title match last week in Washington. He will meet seventh seed Juan Ignacio Chela of Argentina in the final.
Chela outlasted fifth-seeded Spaniard Alex Corretja, 6-2, 2-6, 6-4, in Saturday's other semifinal.
Srichaphan has won nine of his last 10 matches but still has not won an ATP title.
"I've been playing a lot since last week and this is good for me to rest and get ready for the final," he said. "It's like a day off for me. The last couple of months I've been playing consistently and being patient. I've been working hard off the court, as well."
Srichaphan has lost both finals in which he has competed this year. He fell to Argentina's Guillermo Canas at Chennai, India during the opening week of the season.
Chela, who turns 23 next week, defeated Corretja for the third time this year. He also won meetings at the Scottsdale and Indian Wells hardcourt events.
"I think it's better for me to play him on hard court. I feel more comfortable against him on this surface," Chela said. "At the beginning of the match, he didn't look focused, but then he started to play better. I dropped my service twice in the second set and, after the set, I was a little worried."
Chela, who entered the year with a 24-31 career record, reached his third final this season. He won the claycourt event at Amersfoort.