It wasn't until reporters approached Karstens that he learned the whole story -- a MRI taken Friday evening revealed a Grade 1 strain of Wang's right hamstring, knocking the probable Opening Day starter out of commission for most of the season's first month.
The 24-year-old right-hander needed an opening to make the Yankees' pitching staff, but the turn of events was of little consolation to Karstens, who termed it "unfortunate."
"If it was [between] me going to the big leagues or him being healthy, I'd definitely want him to be healthy," Karstens said. "He's an awesome guy."
But as the Yankees come to grips with the reality that they will be sans the services of last year's American League Cy Young Award runner-up, the club has turned its attention to current needs. With Wang down, the Yankees can make use of an additional starting pitcher, and Karstens is as good a bet as any to fill that role.
He has been a standout this spring, going 3-1 with a 2.70 ERA in four appearances (three starts). In 13 1/3 innings, Karstens has allowed 11 hits, struck out 11 and walked none.
Yankees manager Joe Torre said that the team had been looking to make room on its projected 12-man pitching staff for Karstens. While the Yankees will need a fifth starter just once in their first 17 games, Karstens can also be utilized as a long reliever and spot starter.
"I don't want to say it's obvious, but he certainly is the guy who comes to mind," Torre said.
Karstens could wrap up his candidacy for the fifth starter's spot with a strong effort Sunday against the Tigers in Lakeland.
Karstens had reeled off the equivalent of a complete-game shutout, with nine strikeouts in his first three spring appearances, before being touched by Toronto for four runs in 4 2/3 innings in a 9-1 loss at Dunedin on Monday.
"I'm just going to go out there and try to do the same thing I have been doing," Karstens said. "[I want to] be a little better than last time out. They were getting a lot of 0-2, 1-2 hits.
Torre said that he expected New York baseball fans to soon become more familiar with Karstens, a 19th-round selection from the 2003 draft who grew up in San Diego, worked out this winter in Los Angeles with Chase Utley and Nomar Garciaparra, and now appears poised to make his leap to the Bronx.
"At least up until today, he's gone through this anonymously," Torre said. "I have a feeling that he's going to have to answer more questions here in the next couple of days."
Good enough: Mike Mussina came away from his fifth Grapefruit League start satisfied with the results, having settled down after a shaky opening.
"It was better," Mussina said. "It didn't look that great, but I thought it was OK."
Mussina faced eight Blue Jays in the first inning -- a frame extended by a catcher's interference call on Wil Nieves -- and put the Yankees in a 3-0 deficit before Johnny Damon could even lead off. Mussina also allowed a run in the second, but then blanked the Jays on two hits over the next four innings.
He finished a 79-pitch performance having allowed four runs (three earned) and seven hits, walking two and striking out one. He said he was pleased to face the "A" Toronto lineup, which made the half-hour trip from Dunedin and included Lyle Overbay, Vernon Wells, Frank Thomas and Troy Glaus.
"It's satisfying," Mussina said. "They brought over almost all their frontline players. I struggled through the first inning or so, and made some adjustments. We'll just keep going."
No holding back: Given his three-week layoff, Bobby Abreu was in the mood to test his legs Saturday, rounding second base and trying for a triple as he led off the sixth inning against Toronto's Casey Janssen.
Abreu slid safely into third base and said he felt nothing running, another good sign as he continues to put his strained right oblique behind him.
"I just wanted to try it," Abreu said. "I'm starting to make my legs strong. I'll be ready for Opening Day."
The Yankees are giving Abreu a scheduled off-day on Sunday, with Torre telling the right fielder not to report to Legends Field. Abreu has appeared in four exhibition games and has logged 12 at-bats, batting .333. Beginning Monday, he has six contests remaining to hit a personal target of 30 to 40 plate appearances before the regular season.
"You always need the at-bats to work on getting ready," Abreu said. "I'm working on some things."
That's just me: Reliever Jose Veras appeared in the Yankees' clubhouse Friday, his right arm in a sling and a small jar in his hand. Veras had a bone spur removed earlier in the week by Dr. James Andrews in Birmingham, Ala., and was showing off the remainder to his teammates.
Veras pitched 3 1/3 scoreless innings for the Yankees this spring before being sidelined with elbow pain. He is expected to be out for two to three months, general manager Brian Cashman said.
Late scratch: Catcher Jorge Posada was removed from the Yankees' lineup Saturday with what Torre called "overall discomfort," and was replaced by Nieves. Posada is on the travel roster for Sunday, but Torre said he could be scratched again if the symptoms do not improve.
Roster trimming: The number of players in Yankees camp dropped to 39 after Saturday's game. Catcher Raul Chavez, infielders Angel Chavez and Andy Cannizaro, outfielder Bronson Sardinha and left-hander Ben Kozlowski were all reassigned to Minor League camp.
Coming up: The Yankees will travel to Lakeland, Fla., on Sunday to play the second of four scheduled Grapefruit League games against the Tigers. Karstens (3-1, 2.70 ERA) is scheduled to start for New York, with Justin Verlander (0-2, 8.31 ERA) slated to pitch for Detroit. First pitch is set for 1:05 p.m. ET.
Bryan Hoch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.