This malaphor was uttered by Brian Johnson, the San Francisco Giants’ color announcer, describing a Detroit Tigers pitcher.   It is a mash up of “on the ropes” (doing badly and likely to fail) and “back against the wall” (to have serious problems which limit the way you can act).  The speaker may have been thinking of the boxer with his back on the ropes, getting pummeled.  A shout out to Pete Mamalis for hearing this one and sending it in!