He was replaced by Don Kelly before the next inning and later diagnosed with a right foot sprain, the severity of which was not immediately known.
Pirates manager Jim Tracy said there was some point tenderness along the outside of Castillo's foot, and that the plan was to ice it for 24 hours and re-evaluate it afterward with X-rays if necessary.
Castillo's starting spot is in jeopardy this season after his performance dropped dramatically in 2006, subjecting him to scrutiny from fans and teammates alike. Still, he proved himself in Venezuela during the Winter Leagues, hitting for a .308 average that was more than 50 points higher than his Major League season total, and adding five homers and 40 RBIs.
He also dropped more than 10 pounds during the offseason and reported to camp looking and feeling much better. It's unknown at this point exactly how long the injury will set him back, although Tracy was optimistic.
"It seems to be very stable," he said.
Lookin' good: After missing all of 2006 with a broken wrist, first baseman Brad Eldred is making the kind of statement opposing pitchers hate most. He went deep Saturday in the first inning after taking a full-count pitch from New York's Mike Mussina over the wall in left for his second homer in two days. Eldred picked a wild throw from second baseman Freddy Sanchez from the dirt as well, earning him a gold star from Tracy, who said he also admired the way Eldred worked the count in his favor.
"He can hit 'em a long way, believe me," Tracy said. "What I like is the fact that there were at least two pitches that I know of, and possibly three pitches he fouled off and/or took that he may have struck out on. And he stayed off of one or two of them, and fouled another off to the right side, and then got the pitch to swing at and hit the ball out of the ballpark.
"What he's doing this spring, so far, is real good."
Nady update: In the clubhouse Saturday morning, Xavier Nady showed no ill effects of the intestinal inflammation that hospitalized him last week. There still is no update on the cause, which forced him to travel to Pittsburgh earlier this week to have a colonoscopy when blood tests could not determine the nature of Nady's illness.
Nady, a projected starting outfielder along with Jason Bay and Chris Duffy, appeared in good spirits, albeit a little frustrated when discussing his first workout since returning.
"I pretty much did everything you could," Nady said. "I hit, I ran, I took fly balls, and I feel fine.
"It's time for Spring Training, and I want to be out there with everybody else; I want to do things ballplayers do."
Sales soar: Single-game tickets for PNC Park went on sale Saturday morning, and a total of 24,519 tickets were snatched up during the four-hour open-house event at the park, up 52 percent from last year's sales (16,163).
This year, a die-hard fan even camped out at the front gates starting at 11:30 p.m. ET the night prior.
Good eye, Jack: In Tracy's mind, shortstop Jack Wilson fills the No. 2 hole in the lineup better than most because of his cerebral approach. Wilson has done a good job thus far of being aware of who hits after him, National League batting champion Sanchez, and showed his smarts on Thursday against the Reds by drawing a bases-loading walk off pitcher Eric Milton to set the stage for Sanchez.
"Jack knows what to do in those situations, and you like to see that," Tracy said. "That makes an offense real good."
Triumphant return: Before Friday, Bryan Bullington had only seen game action one other time since 2005. Labrum surgery knocked him out of the entire 2006 season, so it was understood when he was a little rusty during his early bullpen sessions.
It didn't take him long, though, to get back into the grove that allowed him to be taken first overall in the 2002 First-Year Player Draft.
"The ball is jumping, and coming out of his hand much better than it was earlier this spring," Tracy said, after Bullington fanned two in a perfect inning on Friday. "I'm sure it's a trend you're going to see because of the inactivity he's had, but he's a very poised-looking pitcher, he's got a very nice delivery. It was great to see."
Bullington credits his workout routine for his quick return and rise, and said once he had his shoulder surgically repaired there were re-evaluations to do and commitments to make.
"Now that I am healthy and trying to maintain that health, I've really got to stay on top of my strength stuff," he said. "I've always taken pride in that stuff anyway, but it gives you that extra focus when you're doing it, that there actually is a purpose for doing it."
Up next: Pittsburgh returns home on Sunday to face Cincinnati for the second time this spring. In addition to the regular 1:05 p.m. ET game, a six-inning "B" game will take place at 10 a.m. at Pirate City.
Righty Shawn Chacon will get the ball for the afternoon contest, where he'll face Homer Bailey. Also scheduled to pitch for Pittsburgh are Masumi Kuwata, Yoslan Herrera, Dan Kolb, Kevin Gryboski and John Grabow.
The Pirates will send left-hander Paul Maholm to the mound to face Cincinnati's Bronson Arroyo during the 10 a.m. game, with Sean Burnett and Josh Shortslef to follow.
The Reds won the first meeting between the two teams, 9-7.
Dawn Klemish is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.