Experiencing physical and/or sexual abuse at the hands of an adult before the age of 15 was reported by 30% of Canadians aged 15 and over. Physical abuse was the most common form of child maltreatment, reported by about one-quarter (26%) of Canadians. Meanwhile, childhood sexual abuse was reported by 8% of people in Canada aged 15 and over. A smaller proportion (5%) said that they had been subjected to both physical and sexual abuse during childhood.
https://www150.statcan.gc.ca/n1/daily-quotidien/170216/dq170216b-eng.htm
A study in Ontario found that 31 per cent of males and 21 per cent of females experienced physical abuse during childhood. https://www.redcross.ca/how-we-help/violence-bullying-and-abuse-prevention/educators/child-abuse-and-neglect-prevention/facts-on-child-abuse-and-neglect
This paper discusses the underreporting problem in detail - https://www.ncbi.nlm.nih.gov/books/NBK195982/
19 percent were physically abused https://www.apa.org/monitor/2008/11/maltreatment
Your first post on the matter said 1 in 7, which is not what your source says "At least 1 in 7 children have experienced child abuse or neglect in the past year in the United States."
As I said the actual number is impossible to determine, but it is at least 15% and based on the information above, likely in the range of 20 to 30%.
Unfortunately, in the USA the stats all relate to reported cases of maltreatment, I can't find anything that estimates the unreported cases.
A good number of MLB players are from dominican, mexico, venezuela - the rate of physical abuse in those countries is estimated to be over 40%.