Placed 6th in the eight-team League, the Nicolas Anelka-managed side need a win in their second-last home game to leap into the top four on the table led by FC Goa with 15 points.
With just one other home game scheduled, against Kerala Blasters on November 26 after tomorrow's match, a lot hinges on the contest - also a revenge clash for Mumbai after their 1-3 humiliation in the away first leg - against Pune.
Mumbai had things going very much their way following a hat-trick of home wins over Delhi Dynamos, FC Goa and North East United FC, before a 4-1 thrashing by last year's champions Atletico de Kolkata upset their rhythm.
The defeat came in a match when marquee player cum manager Anelka shed the latter role to take up the mantle of the main striker.
But this move seemed to have upset the settled combine up front, which included India skipper Sunil Chhetri playing as the central striker, and a big defeat occurred.
Mumbai may not be in the best frame of mind following these happenings and Pune, also seeking a win after the last-gasp 2-2 draw on November 8 at home against table leaders Goa, would be eager to exploit any such weakness.
Pune possess a dependable set of defenders, efficient mid-fielders and good strikers - including marquee player Adrian Mutu who started the match and ended it with a stoppage time goal too against Goa - to turn the tables on a less-than-fully settled Mumbai.