ATLANTA (AP) _ As he has done so many times, Walt Weiss pulled on his uniform, strolled down the long, narrow tunnel connecting the clubhouse to the dugout and emerged on the grass of a baseball field.

A glove dangled naturally from his left hand. A ball fit comfortably in his right.

But after throwing a little, taking a few ground balls and stepping into a batting cage for a handful of swings, a stronger force pulled Weiss away from Turner Field and the game that has dominated so much of his life.

It was his 3-year-old son Brody, hooked to a dialysis machine in an Atlanta hospital, his kidneys stricken with a potentially deadly E. coli infection after a seemingly harmless swim at a water park.

``It's a helpless feeling,'' Weiss said Wednesday before hurrying back to Scottish Rite Children's Medical Center. ``It doesn't seem right that a kid his age should go through something like this. The worst part is the helpless feeling you have.''

Brody's condition has been upgraded from critical to serious, enough improvement for father to leave the hospital for a few hours. After a news conference at Turner Field, Weiss slipped on his uniform for the first time since last Saturday's game at Montreal and took part in fielding drills and batting practice.

But Weiss didn't hang around for the 10-6 loss to the New York Yankees, wanting to get back to his son. He isn't sure when he'll return to the Braves lineup.

``I'm thinking more and more about getting back out there,'' Weiss said. ``I want to play. But my total focus is on Brody's condition. It could change from hour to hour.''

Weiss said Brody seemed much better Wednesday. His eyes were brighter and he was able to talk with his parents. Doctors are hopeful for a full recovery, though the youngster will likely have to be hospitalized for at least a month.

``The most important thing is getting his kidneys operating on their own,'' Weiss said. ``The doctors say there's a real good chance that will happen in the next week or two. When that happens, we've turned the corner.''

He called Brody his ``high-maintenance child,'' which makes it even more painful to see him confined to a hospital bed.

``He's the one who has the most chance of getting in trouble as he grows up,'' Weiss said, a small smile curling on his lips. ``But he's a lot of fun. Everyone always asks about Brody, because there's usually a pretty good story involved. He keeps things very eventful.''

This year was shaping up to be the most eventful of Weiss' career. The 34-year-old is hitting .333 and leads all NL shortstops in voting for the July 7 All-Star game at Colorado.

But the events of June 11 changed all that.

On an off day for the Braves, Weiss, his wife Terri and their three children spent the day at White Water Park, a popular attraction in the north Atlanta suburbs. They frolicked in the cool water and absorbed the warm rays.

Three days later, Brody began experiencing painful diarrhea, prompting the first of four trips to the emergency room. It was nearly a week before doctors diagnosed E. coli, a potentially fatal bacteria.

``The tests showed his kidneys had failed 50 percent,'' Weiss said. ``Once he was diagnosed, the doctors can tell you what's going to happen and there's nothing you can do about it. To watch your child deteriorate over the course of time is frustrating.''

Brody was one of at least eight children who contracted the illness while playing in a kiddie pool at White Water.

Weiss' youngest child, 11-month-old Bo, tested positive for E. coli in his system, but has shown no signs of having the actual illness. He was scheduled to undergo more blood tests today, his father said, and doctors say he should be OK if nothing is found.

The oldest Weiss, 11-year-old Blake, didn't spend much time in the infected pool and showed no indication of being ill.

Weiss said he didn't plan legal action against White Water.

``You have to realize we live in an imperfect world,'' Weiss said. ``I'm not here to place any blame. It's just a freak accident.''

E. coli is usually contracted through eating beef or other food tainted with fecal bacteria. This was the first known case in which people have been infected with E. coli while in a chlorinated public pool, according to the Centers for Disease Control and Prevention.

Weiss said he is heartened by support he's received from the Braves and people he's never met. While standing at his locker Wednesday, teammates approached him one by one, giving him quiet words of encouragement or just a pat on the back.

``It's really scary,'' said second baseman Tony Graffanino, whose son will celebrate his first birthday in three weeks. ``I couldn't imagine going through something like this. I just hope I could handle it as well as he has, but I don't know if I could.''