By Dan Durkin-

(CBS) It wasn’t supposed to be this way.

After finishing second in the league in scoring last season, the Bears maintained continuity on offense with hopes of progress and building on the foundation laid during Marc Trestman’s inaugural season as an NFL head coach. Yet when you watch the Bears offense perform on game day, it’s obvious that this unit lacks confidence. They are playing — and calling — games not to lose rather than attacking their opponent.

With few exceptions, it’s the same mistakes on a weekly basis — pre-snap penalties, missed assignments, inaccurate throws and dropped passes. The psyche of this offense is as fragile as an egg shell, and since they’re unable to pick up the pieces and move on from their self-inflicted wounds, they quickly get out of sync. In turn, that creates a lack of trust from the coaches, which distilled their offense down to horizontal throws, screens and check-downs Sunday in Chicago’s 21-13 win against Tampa Bay at Soldier Field.

Typically, teams script the first 15 plays of the game to both apply schemes they’ve discovered an advantage on through film study as well as to feel out how the defense is going to respond to certain personnel groupings and formations.

At the outset of Sunday’s game, the Bears were predictable, conservative and established no offensive rhythm. The Bucs dictated the line of scrimmage and kept a top on the defense to force everything underneath. Which is exactly how Lovie Smith coaches his team to play defense every week.

Not only was quarterback Jay Cutler not seeing the field well, the routes the Bears were calling were typically short of the line to gain, which requires receivers to catch the ball — typically while standing still with their back to the defense — and turn up field to make defenders miss in order to move the chains.

The Bears’ second drive of the game was a perfect microcosm of their afternoon. A questionable personal foul for roughing the punter put the offense back on the field and what ensued is what has become all too typical.

A dropped pass by Martellus Bennett came on first down. On second down, a formation and motion alert — ghost motion with receiver Marquess Wilson — tipped the Bucs as to what the play call was (key the action of the slot cornerback over Brandon Marshall). On third down, Cutler took the time to survey the field, and he found Marshall on a 15-yard gain to move the chains. Then the Bears were sacked in max protection on a two-man route combination, and a strip sack fumble on third-and-15 — in which Brian de la Puente was simply beaten by Gerald McCoy — gave the ball back to the Bucs.

One step forward, five steps back.

Teams continue to zone the Bears out with two-high safety shells, trusting their ability to stop the run with seven-man fronts, knowing the Bears will shun the vertical passing game and concede with short throws.

The Bears offense was supposed to put the rest of the team on its back and carry them through the season. It’s become the opposite. Games are being conservatively managed to minimize turnovers, but in turn, they’re minimizing the available talent.

Not scoring in the first quarter of six straight games and being shut out in the first half three times in your last five games doesn’t happen by accident. That is a sign of poor preparation by the Bears coaching staff and even worse execution by the players on the field.

The only thing that kept the Bears in Sunday’s game early were booming punts by rookie Pat O’Donnell and an opportunistic defense against an offense that was even worse.

To the chagrin of most fans, it’s been defensive coordinator Mel Tucker who has shown the most imagination and creativity with his game plans over the past few weeks.

Against Tampa Bay, Tucker routinely attacked the assignments and communication of the Bucs’ offensive line by stunting and twisting his down linemen while adding in his linebackers as a fifth rusher to create single-block opportunities. This plan worked like a charm and led to turnovers by Josh McCown on back-to-back plays in the third quarter, which the Bears converted into 14 points on short fields.

The biggest beneficiary of the Bears’ interior tackle twists and stunts was defensive tackle Stephen Paea, who registered two quarterback sacks and three quarterback hits. What was so impressive about Paea’s effort is he was used as the “picker” on the stunts, meaning he’s the setup guy who occupies two blockers to single up the “poster” on the stunt. Yet there Paea was using violent hands and phone-booth strength to split doubles and get to the quarterback.

The Bears’ defensive ends were active as well, as Jared Allen, David Bass, Cornelius Washington and Willie Young combined for seven quarterback hits and two sacks. Bass’s backside pursuit of McCown and subsequent ball punch on a strip sack of him may have been the play of the game.

Chicago’s second- and third-level defenders read their run keys, set hard edges and played the alley as the Bears limited the Bucs to 3.5 yards per carry and made them a one-dimensional attack.

Bears nickel cornerback Demontre Hurst was frequently targeted in coverage and gave up some yardage, but he played a major role in a few key plays. Hurst showed burst to close on a backside blitz to chase McCown down on a third-down play, then stripped the ball from Vincent Jackson at the Bears’ 8-yard line, which was recovered by Tim Jennings, snuffing out a drive that could’ve made it a one-possession game.

Additionally, the Bears got a surge from their special teams units, both in coverage and returns to win the field position battle, which was crucial on a day in which the offense was toothless.

As unconvincing as the last two wins were, the Bears took care of business. However, a true-up of there this team awaits them Thursday in Detroit against the Lions.

On a short week against one of the league’s best defenses, you’ll know exactly where this team is. Given Chicago’s recent performances, it’s hard to believe the Thanksgiving Day game will be anything other than sobering on an otherwise festive day.

Dan Durkin covers the Bears for CBSChicago.com and is a frequent contributor to 670 The Score. Follow him on Twitter at @djdurkin.