assuming their respective win/loss percentages for the season are representative of the likelihood of winning/losing each of the last four games, not adjusting the probability for the wins and losses over the next four games, and not taking into consideration any playoff in the event of a tie (which i think there would be), the probability the cardinals tie the rockies for the second wild card is:
(.519)^4 x (.459)^4=(.0725)x(.0443)=.00314
so, 00.314%.
https://giphy.com/gifs/jim-carrey-dumb-and-dumber-so-youre-telling-me-theres-a-chance-ToMjGpKniGqRNLGBrhu