have another string to (one's) bow
To have an additional option, skill, or ability available to one. At least if you get your degree, you'll have another string to your bow if your football career is short-lived.
have more strings to (one's) bow
To have an additional option, skill, or ability available to one. At least if you get your degree, you'll have more strings to your bow if your football career is short-lived.