Another likeness they share is the underwhelming persona of their coaches.
Silver hair notwithstanding, no one will ever confuse the Cowboys' Wade Phillips with his larger-than-life predecessor, Bill Parcells, who still gets far more national-television face time on commercials and ESPN.
When the Cowboys hired Phillips last February, there was talk in many league circles that he was merely keeping the seat warm for someone else. Although Phillips was highly regarded for his defensive expertise, his head-coaching record left something to be desired. After a year or so, the speculation went, owner Jerry Jones would either promote the offensive coordinator he hired on his own, Jason Garrett, or go after a prominent outsider, such as former Steelers coach Bill Cowher.
Now, Phillips and McCarthy are enjoying the kind of success that has made them the envy of all but one member of the league's coaching fraternity -- Bill Belichick, whose New England Patriots are 11-0.
Each has played an important role in putting their teams in position to play for NFC supremacy on Thursday night at Texas Stadium. Phillips has brought his attacking, playmaking version of the 3-4 defense to Dallas, replacing the more reactive version Parcells put in place. McCarthy has put together a highly effective passing game that ranks second in the NFL.
Yet, the favorable results these coaches have generated have as much to do with their personalities as it does with the way they configure Xs and Os.
Phillips and McCarthy make a point of putting their players well ahead of their own egos. Some of the men in their profession dread being labeled a "players' coach," because it carries the connotation of being a pushover and having no control over the team. Phillips and McCarthy embrace it.
When asked recently about who deserves more credit for the Cowboys' dominance this season -- Phillips or Parcells, who put many of the key pieces in place -- Phillips said, "No. 1, it starts with the players."
It was the same approach Phillips took during previous head-coaching stints with Denver and Buffalo, and on an interim basis with Atlanta. He is plainspoken and folksy, just like his father, former Houston and New Orleans coach "Bum" Phillips.
Wade Phillips is always quick with a smile and a joke. He believes in creating a fun atmosphere for practice, on the theory that it does more to hold players' attention than a rigid environment. He likes rewarding players by giving them the Monday off after a Sunday victory.
It is a stark contrast to Parcells' high-pressure approach, which was designed to keep players, coaches, and everyone else connected with the team on edge and always looking over his shoulder.
One player who has responded particularly well to the change is Terrell Owens, who is having a tremendous season as a consistent big-play target for Tony Romo. Known for being a disruptive force who thrived on drawing attention to himself, Owens had clashes with Parcells and former Cowboys passing-game coordinator Todd Haley. Despite leading the team last season with 85 receptions for 1,180 yards and an NFL-high 13 touchdowns, Owens found little joy because of his turbulent relationship with his coaches.
Upon Phillips' hiring, many NFL analysts presumed that if Owens were still on the team (his Cowboys future was uncertain at the time), he would run roughshod over his kinder and gentler new coach. Instead, Owens has conducted himself as well off the field as he has on it. He is a happy and positive force, which Phillips has done plenty to help develop by making it an immediate priority to get the ball in Owens' hands as much as possible and by allowing his top receiver to feel far more comfortable than he did around Parcells.
"(Owens) was the first guy to call and congratulate me when I got the job," Phillips said. "We got off on a good foot right there."
"I have a renewed sense of focus, determination and passion for the game, things I felt kind of got left by the wayside last year," said Owens. "I'm just going out and playing stress-free football."
McCarthy has had a similar impact on the Packers with a straight-forward, no-nonsense style. He treats his players like men, even though his roster has gotten younger since he arrived. He emphasizes toughness, mental and physical, and his squad has performed accordingly.
Never was that more apparent than the way the Packers responded to their 4-8 start last year. They proceeded to win their final four games and have gone on to share the league's second-best record with Dallas. At 18-9, McCarthy has had the best start among active coaches as well as the best in Packers history, surpassing the 15-10 mark of Vince Lombardi.
McCarthy's most notable achievement is his handling of Brett Favre. After McCarthy replaced Mike Sherman, there was concern that he might not be able to get through to Favre, whose legendary status made him more important than anyone else in the history of the franchise, short of Lombardi.
However, McCarthy managed to convince Favre to play with greater discipline and structure, avoiding many of the risks that he once took. By keeping mistakes to a minimum, Favre has performed as well as ever. He has delivered his customary game-breaking throws, but he also has played with enough efficiency to overcome the league's last-place running offense and complement a strong defense.
He could have been talking about Phillips as well.