Not 100 percent sure if this is how it works, but my husband worked in Canada 7ish years ago and this is what happened.
A non-resident is usually required to pay Canadian tax only on Canadian sources of income; however, under the income tax treaty between Canada and the U.S., a worker may be exempt from Canadian taxation and may apply for exemption on withholding of tax from Canadian sources.
If the taxpayer is working in Canada, but for a U.S. company, and is paid by the U.S. company, employment income is exempt from Canadian taxation as long as the taxpayer is not residing in Canada.
I am not sure if the Raptors are considered a U.S. company since they are obviously in Toronto, but they are part of the NBA and that might be a US based company. Obviously it is murky and I am not a CPA.