After struggling in the second half in their first two games, the Bears got dominated on both sides of the ball in the first half of Sunday night's 31-17 loss to the Cowboys.
"You have to put a complete game together and we have not done that through the first three games," Fox said Monday after watching tape of a defeat that dropped the Bears to 0-3.
Starting in place of the injured Jay Cutler, Brian Hoyer completed 30 of 49 passes for 317 yards with two touchdowns, no interceptions and a 93.7 passer rating. But 246 of his yards came in the second half when the Bears never trailed by fewer than 14 points.
"I thought he made good decisions, not all of them," Fox said. "The very first play of the game didn't go quite as smooth as we'd like. [But] I thought he did some good things. I thought the pass pro and some of those things helped the situation.
On the Bears' first play from scrimmage, Hoyer failed to hand the ball off to running back Jeremy Langford and was tackled for a one-yard loss.
"It was a run-pass option and I probably should have given it," Hoyer said. "That's something I definitely need to correct. We talk about early struggles. We just hand it off and see what Jeremy can do, but it was a run-pass option. It's on me and I should have handed the ball off."
Fox said Monday that the Bears are "kind of in a day-to-day mode" with Cutler, who missed the Cowboys game with a sprained thumb he sustained a week earlier in a loss to the Eagles.
Asked if Cutler will return as the team's starting quarterback when he's healthy, Fox said: "I don't think there are any givens, and that's no indictment on anybody. This is a day-to-day, week-to-week, what-have-you-done-for-me-lately league and so we're just trying to get the best 11 guys out there regardless of the position to where we can play a full 60 minutes and get a victory."
The Bears had two long runs Sunday night—a 36-yarder by Jordan Howard and a 23-yarder by Jeremy Langford—that accounted for 59 of their 73 yards on the ground.
Asked about the team's rushing attack this season, Fox said: "It's hit and miss just like us. Really in all three phases I think there have been some positives. I don't think we've put a complete game together by any stretch. I think that's evident. Whether it's the run game, the run defense, the pass game, the pass defense, obviously none of it's been good enough."
Receiver Kevin White, who missed his entire rookie season last year with a leg injury, had his most productive game to date with six receptions for 62 yards.
"I think all young players, the more they do it, the better they're going to get," Fox said. "We've got a lot of young ones out there. Whether you're talking about [center] Cody Whitehair or Kevin White or [linebacker] Nick Kwiatkoski, they're figuring it out on the fly and Kevin, over the first three games of the season, I think he had his best game."
The Bears defense generated little if any pressure on Cowboys rookie quarterback Dak Prescott, who made plays with his arm and legs. The fourth-round draft pick passed for 248 yards and one touchdown and rushed for 36 yards and a second TD on four carries without being sacked.
Asked if the Bears were concerned with Prescott's mobility, Fox said: "We were concerned with all of it, with their offensive line, it's one of the better ones in the league.
"You combine that with a mobile quarterback and some matchup problems maybe at other positions, even in the skill positions, it was going to be a challenge for us, especially with some new guys starting for the very first time, some of them playing for the very first time in a real NFL game. But I think they learned from it; there will be some positive experiences from it."
Playing without injured veterans Danny Trevathan, Pernell McPhee, Lamarr Houston, Eddie Goldman and Kyle Fuller on defense, the Bears had to rely on several young untested players.
"Obviously we liked them well enough to bring them here as part of the 53," Fox said. "Nobody comes and rescues you. We just have to get better and get better quickly. I think the mindset and the leadership in that locker room will help that and I have confidence that we'll improve."