"Jugar" always requires the preposition "a" (followed by "al" for masculine gender sports or games or by "a la" for feminine ones) in all Spanish speaking countries except for Mexico where the "a" may or may not be omitted. This page (http://laspreposiciones.com/verbs-and-prepositions.html) explains verbs that require the preposition "a" as "springboard verbs" because they mark the beginning of an action. It lists a number of other verbs (jugar is omitted though it follows the same rule) that are always followed by the preposition "a". These are verbs that "move toward an action [as in the case with jugar] or lead a person ahead, either literally or figuratively. Remember that the preposition a means "to", and that when you go to something, you are moving ahead, going forward."