In mid-October, there was little to suggest that Daniel Flores, a friendly, highly regarded Red Sox catching prospect from Venezuela, was anything but healthy.
He was playing in the Dominican Republic instructional league as recently as Oct. 24, a strapping 17-year-old who landed a $3.1-million signing bonus from the Sox in July and who won over friends among the young Sox prospects in Fort Myers and the Dominican in the months since.
Then came a piece of seemingly impossible news Wednesday: Flores died of what the Red Sox described as complications from treatment for cancer.
Thursday night, a close family friend said Flores was diagnosed in late October with testicular cancer that had metastasized.
The friend, trainer José Salas Jr., differed slightly with the team’s account of the death, saying he did not know of complications arising from the treatment. Salas was in Boston with Flores’s mother, who had flown here with her son on Oct. 28 after Flores complained of lower back pain.
“There’s nothing much to say,” Salas said in an interview, his voice cracking. “Two Tuesdays ago he was hitting line drives to 95 mile-per-hour fastballs.”
Salas said Flores had attributed the back pain to a pulled muscle or “just a bad night.” He would be dead within days of the diagnosis.
“When we saw it was bad, we did CT scans, X-rays, and stuff, and it was way too late, it was already too late,” Salas told the Globe Thursday night. “He was so strong that he wouldn’t feel pain. . . . There were no indications, nothing suspicious, no negligence, there was nothing. . . . I don’t know what to tell you.”
A catcher with his size (6 feet 2 inches, 220 pounds), hands, footwork, agility, and offensive ability inspired comparisons to catchers such as Royals All-Star Salvador Perez and Red Sox great Jason Varitek. For a player of that potential, the Sox invested $3.1 million in July — the second-highest bonus ever for an amateur from Venezuela and the largest bonus for an international amateur catcher.
“You literally couldn’t have been able to see that he was in that condition at all,” said Alex Scherff, a Red Sox pitching prospect who had befriended Flores over the past few weeks.
“He completely dominates the game,” said Scherff, a 19-year-old whom the Sox took out of high school in the fifth round of this year’s draft. “He’s the best catcher I’ve ever seen, no doubt in my mind at all.’’
He recalled that Flores was easy to talk to, and “very forgiving with how my Spanish was.’’
“[In Fort Myers] he was very shy, but when you got him to open up, he was really nice, very funny — a huge joker. In the Dominican, he was a leader. All the guys really looked up to him.’’
Flores, who had caught the eye of scouts at age 14, was wasting no time asserting himself as a prospect of unusual skill as well as maturity. That combination led most evaluators to consider him one of the top two prospects in this year’s international amateur free agent class.
“He knocked balls off the wall every time he was at the plate,’’ said Scherff. “He just made it look so easy.”
That Flores would sign as a 16-year-old — the youngest age at which players from countries outside of the United States and Canada can sign — was a given. “He was always wearing a Red Sox hat,” recalled one evaluator of his 2016 introduction to Flores, then 15.
He’d moved from the island of Margarita to Caracas to work with trainer Salas, who became so close to Flores that the catcher, according to agent Cesar Suarez, referred to him as “dad.” At Salas’s Academia Puro Beisbol, Flores became well-known.
Before agreements with prospects — whether draftees or international teenagers — become official, players must take a physical. According to major league sources, for lower-dollar signings, the physical might take place either in the player’s home country or at a team’s academy in the Dominican Republic. For larger commitments such as that signed by Flores, it’s more common for a complete medical workup to happen either at a team’s spring training facility or in the city where the team plays.
While each team conducts physicals differently, standard elements for a catcher might include MRIs on the shoulders, throwing elbow, and potentially knees, plus blood work, and in some cases EKGs to monitor heart function. While the specifics of the Sox’ procedures were unclear, one National League source said that the team has a reputation for being “pretty extensive” in its medical evaluations.
Complete medical records often are harder to come by, sometimes leading teams to include contractual outs in case a preexisting condition is discovered after a player signs. Most teams conduct their physicals just before or just after the agreement becomes official, which, in Flores’s case, happened in July.
Salas said that all of Flores’s blood work as well as all of his physical exams before signing the Red Sox contract came back clear.
“No signs, no follow-ups, no nothing. . . . We did every little test and he was fine,” Salas said.
When Flores’s deal with the Red Sox was announced, it was national news in Venezuela, with the then-16-year-old taking part in a press conference that was broadcast throughout the country. Wearing a Red Sox jersey, he addressed “all the little children who are listening.”
“This is the most important thing,” he told them. “This is the game of baseball. It’s fun. Have fun because that’s more important than anything else.”
By all accounts, Flores was living out that advice in the early months of his professional career.
“He was just such a nice kid,” said shortstop C.J. Chatham, who got to know Flores in Fort Myers. “He always smiled while he was trying to understand what you were saying. He was always energetic. He was just such a great person.”
Salas said Flores helped lift his mother, Rosa Urbaneja, and his 10-year-old sister out of poverty.
“Daniel Flores taught us a lot of things,” Salas said. “Humor, confidence, willpower — what a willpower, wow, what a willpower. . . .”
“Honest, sincere, a hard-worker, an excellent son who was always smiling,” Salas said. “He didn’t get to the majors in baseball. In life, he’s a Hall of Famer.”
“It’s just unreal. He was a guy that everyone should have known,” said Scherff. “He was just special. It’s hard to explain what that means, but he was just a really special guy. You could tell by watching him play and talking to him, he was just destined for more. To see him go like that out of nowhere, it’s something you never thought would happen.”
Maria Cramer of the Globe staff contributed to this report. Alex Speier can be reached at email@example.com. Follow him on twitter at @alexspeier.