NEW YORK -- After having medical tests done the past two days to figure out what has stolen the speed from his fastball, Phil Hughes is going to see a specialist to determine if he has thoracic outlet syndrome, according to Yankees manager Joe Girardi.
In one of the tests Hughes underwent, Girardi said there was a low-level frequency of the syndrome.
"We are not saying that he has it," Girardi said. "We are not saying that he doesn't. A real low-level risk of thoracic outlet syndrome, which is basically a circulatory problem."
After Hughes wasn't able to clock a fastball consistently above 90 mph in his first three starts, the Yankees put him on the disabled list on April 15. They described his condition then as right arm inflammation and a "dead arm."
According to Web MD, "thoracic outlet syndrome [TOS] is a condition presenting with arm complaints of pain, numbness, tingling and weakness. The cause is pressure in the neck against the nerves and blood vessels that go to the arm."
If Hughes does have the condition, Girardi did not know what the timetable would be for his return. Other major leaguers, including Kenny Rogers in 2001, have been diagnosed with TOS. It can require surgery, which would cause Hughes to miss a significant amount of time.
"I think anytime you talk about circulation problems, there is some concern," Girardi said.
Hughes will meet with Dr. William Thompson in St. Louis soon to find out if he does in fact have TOS.
On Wednesday before Girardi made the announcement following the Yankees' 3-1 win over the White Sox, Hughes underwent a dye MRI, CT scan and myriad of other tests at New York Presbyterian Hospital. Hughes said he spent five hours at the hospital.
On Tuesday, Hughes also underwent two MRIs and an ultrasound test on his right arm to check blood flow and circulation.
"I'm ready to figure out what it is, fix it and get back to throwing," Hughes said. "I hope it's not something that sets me back too much. Hopefully it's something minor and fixable and something that will get me back to being what I know I can be.
Hughes said he's been shut down until further notice, but he did run on the treadmill Tuesday.
Hughes was supposed to make a rehab start Thursday, but suffered what Girardi referred to as a "setback" after throwing 20 pitches during a bullpen session Monday afternoon.
Hughes is 0-1 with a 13.94 ERA in 2011. He's given up 16 runs on 19 hits in 10 1/3 innings, while allowing four home runs and striking out just three batters.
According to FanGraphs.com, Hughes' fastball has averaged just 89.3 mph this season. His average fastball was 92.5 mph in 2010 and 93.8 in 2009, according to the website.
Hughes was named to the American League All-Star team last season, when he finished 18-8 with a 4.18 ERA. However, Hughes struggled mightily in the second half of 2010, going 7-6 with a 4.90 ERA after closing the first half 11-2 with a 3.65 ERA.
Hughes logged a career-high 176 1/3 regular-season innings in 2010, 90 1/3 more than he completed in 2009 (86).
Scouts first began to notice the diminished velocity on Hughes' heater during spring training.
Andrew Marchand covers the Yankees for ESPNNewYork.com. Mike Mazzeo is a regular contributor to ESPNNewYork.com.