Far from it.
If Dallas loses Sunday night, but wins their last three games, the Cowboys win the division. In fact, if the Cowboys lose Sunday night and Saturday night at Tampa Bay, but beat the Eagles and Giants, the Cowboys still win the division regardless of what New York does. Both teams would be 9-7, with Dallas having a better division record (4-2 to 3-3).
If the Cowboys lose to the Giants twice, Dallas would need to beat both Tampa Bay and Philadelphia and hope that New York loses to both the Redskins and the Jets. "So you're saying there's a chance..." Dallas would be 9-7 and New York would be 8-8.
If Dallas loses Sunday night, but splits the season series with New York by winning in the New Meadowlands, the Cowboys only need help if they lose to the Eagles. Dallas would be 3-3 in the division, and either need the Giants to lose to Washington (making them 2-4 in the division), or lose to the Jets (meaning that the Cowboys and Giants have the same record against similar opponents [third tie-breaker], but Dallas has a better NFC record).
If the Giants win Sunday night and lose to EITHER the Redskins or Jets (the Jets are making a strong playoff push), the Cowboys could lose to BOTH the Buccaneers and the Eagles and still win the NFC East (if the Eagles lose one more game: like this weekend against Miami). In this case, the Eagles would be no better than 7-9, and the Giants would be 8-8 with the Cowboys but lose due to division record or NFC record (see previous paragraph).
So this game is far from a must win for the Cowboys. On the other hand, if the Giants lose Sunday night, New York needs help from the Eagles to win the division, and have to win the last three games. A win by Dallas on Sunday night, combined with a win by the Cowboys over the Eagles would ensure that Dallas would have no worse than a 4-2 division record, and New York could do no better than 3-3 in the division.
A Dallas win on Sunday night with a loss by New York to either the Jets or the Redskins, eliminates the Giants from the division title. Again, the Giants would lose the tie-breakers by having a worse divison record or a worse NFC record.
A win by Dallas on Sunday night with either one more win in the regular season or an Ealges loss, eliminates the Eagles from the division title. The Eagles would have 9 losses, while Dallas would have 8 wins.
In other words, if the Eagles lose one more game (say to a hot Miami team this weekend), Dallas beats the Giants on Sunday night, and the Giants lose one more game (to either the Redskins, Jets or Cowboys), the Cowboys win the NFC East.
While this Sunday night is not a must win, it would all but eliminate the other teams from winning the NFC East.
By the way, Dallas holds the tie-breakers against Atlanta, New Orleans, and San Francisco for the number 3 and number 2 seeds...if it gets to that.
Plenty to watch this weekend.
What's the phrase? Oh yeah...
FEAR THE STAR!
(BTW, all Cowboys fans know that Tuck really does have Star envy. Considering the parallels between Freud's penis envy theory: it really is about your manhood!)