The pitcher spent the night at Harborview Medical Center under the care of Dr. Richard Ellenbogen, chief of neurosurgery at the hospital. Soriano had an X-ray and two CT scans that revealed no fractures or internal swelling of the brain.
Other than being tired and still having a slight residual headache, Soriano was doing quite well.
"He was pretty articulate in both Spanish and English with staff and he is in pretty good spirits," Ellenbogen said. "I did not know him before, but his family doesn't think he's lost very much."
With one out in the eighth, Guerrero lined a first-pitch fastball and the ball ricocheted off Soriano's head into foul territory along the third-base line. Soriano tried to protect himself but couldn't get his glove up in time.
The sound of the ball hitting Soriano was audible throughout the stadium. He was on the ground for several minutes as the Mariners' training staff and medics rushed to the mound. He was later taken off the field on a cart and taken to the nearby hospital.
Guerrero visited Soriano in the hospital for about five minutes Tuesday night. The two are friends from the Dominican Republic.
"I feel a whole lot better knowing he's OK," Guerrero said.
Seattle won 6-4, its sixth straight victory, but Soriano's injury muted any celebration. Manager Mike Hargrove, pitching coach Rafael Chaves and general manager Bill Bavasi joined some of Soriano's family at the hospital immediately after the game.
"You see somebody hit like that, it's somebody's worst nightmare," Hargrove said before Wednesday night's game.
Soriano was fortunate to be hit where he was, Ellenbogen said, noting that some of the thickest bone in the skull lies behind the ear. Television replays showed that Soriano braced for the impact, if only for a slight moment.
"He's fortunate it didn't hit him in the orbit, eyeball, nose or any of the softer places of the skull," Ellenbogen said. "Although he wasn't in the right place at the right time, it was better than it could have been."
Doctors plan to re-examine Soriano in 10 to 14 days, and the team has set no timetable for his return, but Hargrove seemed to think Soriano would be back this season. With rosters expanding on Sept. 1, the Mariners chose not to put Soriano on the disabled list and add a minor-league pitcher to the roster for Wednesday's game.
Seattle has an off day Thursday and opens a road trip Friday against Tampa Bay.
Mariners players cringed and moaned as images of pitchers getting hit with batted balls played on large televisions in their clubhouse before Wednesday night's game. Chaves said he's surprised it doesn't happen more often with the poor fielding position many pitchers put themselves in on their release.
But Seattle's pitchers realized it was something they couldn't dwell on.
"It's something you have to put out of your mind," left-handed reliever George Sherrill said. "You're never going to be an effective pitcher if you're pitching scared."