The Stars are priced at 25/1 to win the Big Bash League but Cartwright believes unless they beat the Heat on Sunday they can forget about it.
Cartwright was speaking after the Stars slipped to a 23-run defeat against the Adelaide Strikers at the Adelaide Oval on Saturday, and he says their BBL11 campaign is dangling by a thread.
The Strikers batted first when posting 5-155 and then managed to restrict the Stars to 8-132 with Henry Thornton the star bowler with figures of 4-26.
Cartwright himself took matters into his own hands and only a fine innings of 49 runs prevented the defeat from being even heavier.
Now all eyes turn to Sunday and a must-win game against the Heat at the MCG, and they should be boosted by the return of fast bowler Nathan Coulter-Nile.
"It always makes it tough when no-one in the top four is there towards the back end to bat around," said Cartwright. "Everything's on the line tomorrow. If we drop that game, that's us done. It's more or less make-or-break."
The Strikers have now won three games on the bounce and are emerging as dark horses to contend for the BBL11 title.
Jonathan Wells who had smashed a career-best total of 73 believes they could be peaking at just the right time.
"It was a huge game for us - two teams battling for that finals spot," Wells said. "We knew 150-155 was defendable.
"I think we've still got some improvement to do but you want to be playing your best cricket at the back end."