By Dan Durkin—

(CBS) The NFL preseason is a necessary evil. It’s a paradox in which you’re happy to see football back on your television, but you’ll be just as happy once it’s over.

Thursday night’s Bears-Dolphins game was filled with requisite sloppiness, vanilla schemes and limited appearances by the players who will matter most once the regular season starts. The fact that Chicago is 1-0 after beating Miami, 27-10, means nothing. However, there were some impressions to be drawn.

Basing the game on what you saw when both teams’ starting units played, the Dolphins had a much better showing on both sides of the ball. On a macro-level, there are some immediate, big-picture concerns for the Bears.

Bears notebook: ‘Sloppy’ but productive start for Chicago

Defensively, the Bears’ first-team defense lacks speed.

It was apparent on several occasions. The Bears were beat to the perimeter on runs and were steps behind receivers in coverage. This can be attributed to their age at certain positions, as well as the overall uncertainty of playing in a new scheme. But finding reasons why doesn’t solve the underlying talent issue.

Free agent acquisitions Antrel Rolle and Pernell McPhee lost backside contain, and linebackers were misaligned on a gash run by Dolphins running back Lamar Miller. Cornerback Kyle Fuller was a step behind in man coverage, leading to a chunk play in the pass game.

The Brock Vereen-at-strong-safety experiment got off to a bad start. He was late to react in coverage and was then discarded near the sideline on a tackle attempt, which led to extra yards. Dolphins quarterback Ryan Tannehill had a near-perfect evening. He consistently threw the ball from clean pockets, as the Bears were unable to generate any semblance of a pass rush.

Techniques and assignments can be cleaned up. That’s one of the biggest benefits of the preseason: the game film the coaches will now grade and review with their players. However, the overall lack of speed can’t be solved.

Offensively, the line – in particular the starting tackles – struggled.

Granted, the Bears were playing without two of their best players, wide receiver Alshon Jeffery (dealing with a calf strain) and running back Matt Forte. However, the quickest way for a defense to neutralize another team’s weapons is to control the line of scrimmage, which the Dolphins’ starting defensive front did.

Jordan Mills started the preseason off in midseason form with a false start. Call it nerves if you want, but it certainly had a lot to do with the man lining up across him, Cameron Wake. Just like last season, Wake had his way with Mills in every pass rush set. Wake’s sack of Jay Cutler was nullified by a penalty, but that set showed everything that’s wrong with Mills’ game: slow out of his stance, off-target with his punch and off-balance with his anchor.

Opposite of Mills, Jermon Bushrod had a few physical breakdowns in which he was knocked off his anchor, leading to stalled feet and conceding the edge. I’ve highlighted the offensive line concerns all offseason, and they were on full display against Miami – one starter short and no depth.

Offensive coordinator Adam Gase spread the Dolphins out, running a lot of three- and four-wide shotgun sets in an up-tempo fashion. Part of this decision may have been to see how his offensive tackles held up on an island without help.

They needed a life preserver Thursday night.

In the regular season, help will come in the form of in-line tight ends and check releases by running backs, but that limits the number of receivers out in routes.

Bernstein brief: The Bears need a lot of work

Outside of the sloppy showing by the starters, there were some strong individual performances.

The Bears’ best player who played and dressed – guard Kyle Long – was exceptional. He plays with strength at the point of attack to own his gap, flows with ease on lead traps and has fluid feet to mirror and wall off pass rushers. With the tackles struggling, the question of when Long may kick outside becomes even more prevalent.

Role players like cornerback Sherrick McManis, defensive lineman Will Sutton, quarterback Jimmy Clausen, outside linebacker Sam Acho and running backs Ka’Deem Carey and Senorise Perry will grade out positively for their performances.

McManis has been known as a special teams player but was physical as a force player in the run and forced a fumble. After the top three cornerbacks – Fuller, Tim Jennings and Alan Ball – the position is wide open. He was already a near-roster lock due to his special teams prowess, but he has now put himself into consideration as a dime sub-package player.

Sutton may not fit the physical profile of a 3-4 defensive end, but his quickness on the edge and burst to close led to several flash plays. The Bears need solutions to their rotation issue along the defensive line, and Sutton took a very positive step Thursday night.

In training camp, the backup quarterback position has been a consistent concern. However, Clausen was given extensive playing time and made the most of it. Casting statistics aside, he was decisive with his reads and delivered the ball on time, accurately and kept it out of harm’s way. It was encouraging to see him operate the offense with confidence.

In a crowded outside linebacker position, Acho had a standout evening. On his sack, he used excellent technique with his hands to swipe and rip to gain the edge, then finished the play. He capped off his evening with an interception that led to a touchdown. He also played on the kickoff coverage unit; don’t discount that detail, as it will be an important factor as final roster decisions are made.

The Bears are likely to carry four running backs on their roster. With Forte and Jeremy Langford locks to make the roster, Carey and Perry must earn their way onto the roster. As a pure running back, Carey is a better player and prospect. The Bears lack a short-yardage runner, which may benefit Carey, who was decisive with his runs and pressed the line of scrimmage. But Perry broke a big touchdown run and plays special teams.

The preseason is meaningless in terms of record and what it portends to the regular season. However, performances in Thursday night’s game earned and cost middle/bottom-of-the-roster players snaps in the team’s next preseason game on Aug. 22 in Indianapolis against the Colts.

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