You mean like when Murray averaged 2.6 ypc in the key season ending games/wins against Philly and Indy? It wasn't all peaches and cream for Murray last year either, especially in some key games. He averaged only 3.7 ypc in that debacle on T-giving as well.
It's also a bit disingenuous to not at least acknowledge that it was probably tough running in games this year against good teams when there's no threat from the QB and WR.
IMO, I think McFadden can well be the lead back behind this OL with a competent QB and get this team to the SB. My fear would not be in his skill but rather his health. Last year was the first year he seemed really healthy in a long time. I'd worry that last year would be our lucky year healthwise and he's revert to nicked up McFadden in 2016.
Why point to those games when we won them? Murray only had 3 down games all season in 2014 and they came late in the season when he was wearing down from a franchise record number of carries. McFadden's poor games came in critical games some earlier in the season when he should have been fresh from not receiving many carries. Our inability to run the ball contributed to those losses. Murray never averaged less than 4.1 a carry in the first 11 games of the 2014 season while McFadden averaged under 4.0 a carry in 8 of his first 12 games in 2015. It took 12 games before Murray averaged under 4.0 a carry in 2014 despite defenses trying to stop him.
McFadden had 2 games this past season where he didn't even average 2.0 a carry. Murray only had 3 games in 2014 where he averaged under 4.0 a carry and those games came late in the season. Despite Brandon Weeden playing a very good game vs an 0-3 NO team McFadden averaged only 3.1 a carry on 10 carries which contributed to that loss. Weeden had a 105.6 passer rating in that game and got us into OT on a last ditch length of the field drive. The poorest game McFadden had all season was against a bad Bucs team that went 6-10 resulting in their head coach getting fired. On 17 carries McFadden averaged only 1.9 a carry.
I'm not going to pin some of the bad games McFadden had on our QB or WR situation because even in some of the games Romo and Dez played he didn't produce. He didn't start producing consistently until the final 4 weeks when our season was done and we were playing with Kellen Moore the final 3 weeks. When the games still mattered he didn't produce consistently especially in short yardage situations. According to some now a great OL isn't enough for him to produce he needs a competent QB. When he had a competent QB this season he played one solid game.