Your liability for income tax in Canada is based on your status as a resident or non-resident of Canada. Your residency status must be established before your tax liability to Canada can be determined.
If you are considered to be a non-resident of Canada, you are generally taxed only on income from sources within Canada, such as your CFL salary.
If you are considered to be resident of Canada, you are generally subject to Canadian tax on your worldwide income. However, if you have income that is sourced to the U.S. or other countries, you are generally eligible to claim a credit against your Canadian tax for the tax paid to the other country.