Millen expressed regret in the decision to fire Mariucci, but the 4-7 record, the 27-7 loss to Atlanta on Thanksgiving Day and the Lions' failure to live up to expectations left him with no choice.
"We started off this season with high expectations, and I believe that this was a roster that was capable of making a playoff run, and I still believe that," Millen said. "Quite frankly, we have not lived up to our expectations.
"I believe we have underachieved as a football team, and I also believe that we have not developed our younger players, and that is bothersome, especially in the way that we had anticipated going."
Millen said he made the move with five games remaining with the hope of salvaging something of the season and developing the players who were not progressing on schedule under Mariucci.
Although Millen did not identify the young players he feels have not been developed, there are three glaring candidates — running back Kevin Jones, wide receiver Charles Rogers and rookie wide receiver Mike Williams.
Jones, who had a strong second half of last year's rookie season, has had 20 carries or more only three times in the Lions' first 11 games. In the Atlanta game, he carried only four times.
Rogers missed four games when he was suspended under the NFL's substance-abuse program, and he has been used sparingly since returning to action. Williams was not active in the Nov. 20 game at Dallas. All three are first-round draft picks that Mariucci seemed reluctant to use.
It is believed the Lions also want to see four-year veteran Joey Harrington in a conventional offense to determine whether he is still a viable long-term candidate to quarterback the team.
The Lions had records of 5-11 and 6-10 in Mariucci's two full seasons. They were 4-7 this year, well below the nine- or 10-win total that they were anticipating.
Millen also fired offensive line coach Pat Morris and tight ends coach Andy Sugarman.
Quarterbacks coach Greg Olson, who had success calling plays the final three games of the 2004 season, will handle that responsibility again. Ted Tollner, the offensive coordinator under Mariucci, will work with Olson and also with the team's tight ends. Sean Kugler will replace Morris as the line coach.
"I don't think anyone in our business wants to be standing here in this situation that I am standing in front of you," Jauron told reporters. "In this situation, it is even a little bit different for me because Steve and I are friends and we do have a history together, and we kind of started in the business at about the same time ..."
Jauron said he talked with Mariucci before accepting the position Monday morning after Mariucci was fired by Lions president Matt Millen.
Millen, who was fined $250,000 for failing to interview a minority candidate at the time he hired Mariucci three years ago, said he had no commitment to Jauron beyond the remaining five games of the season. And Jauron said he was not thinking beyond the game Sunday against Minnesota.
"We need to take these next five weeks and we need to play and we need to play as well as we can play, perform as hard as we can perform and see what we can get out of it," Jauron said. "We will play them all to win, we will play every game to win, and we will take them one at a time."
When the Lions opened the season with a 17-3 win over Green Bay, they felt they were on the way to fulfilling the high expectations growing out of their offseason player acquisitions. Since then, however, they have had three two-game losing streaks and have been unable to put together back-to-back wins.
At least one player — quarterback Joey Harrington — disagrees with those who feel the team's play has deteriorated in recent weeks.
"I don't think we've played worse and worse," Harrington said, in response to a reporter's question. "We've played consistently poorly all year long.
"Is it a shock to me? Yeah, of course it's a shock to me. Everybody had higher expectations. Some more realistic than others, but everybody had higher expectations than whatever we are right now — 4-7."