By Dan Durkin-

(CBS) Heading into Sunday night’s game against the 49ers, the Bears were already dealing with a litany of injury issues, forcing weekend roster shuffling and game-time decisions involving their star players. They endured even more throughout the course of the game, losing three starters, yet showed grit and resolve to gut out huge a 28-20 win and spoil the first ever game at Levi’s Stadium and even their record at 1-1.

It was a tale of two halves. In the first half, the Bears couldn’t get out of their own way. From shoddy special teams play to a sputtering offense, the Bears had no rhythm and dug themselves an early hole.

For the second straight week, the defense was put in a bind due to other phases of the game. A blocked punt on the opening drive of the game and a botched shotgun snap set the 49ers up with short fields. They only had to travel only a combined 38 yards on their two touchdown drives.

However, for the second straight week, the defense held the opponent to a combined three points in the third and fourth quarters and kept the Bears in the game long enough for the offense to find its way.

Knowing the Bears receivers weren’t playing at full speed, the 49ers’ secondary sat on routes, keeping a shallow top on the defense to keep everything underneath. They challenged the Bears to put together long drives to score, and their plan nearly worked for the entire first half.

Down 17-0 with a little more than two minutes left in the half, the Bears’ offense showed signs of life.

Quarterback Jay Cutler took it upon himself, orchestrating an 80-yard up-tempo scoring drive. On a two-man (man under, two deep safeties) look from the 49ers, Cutler broke the pocket and scrambled 25 yards for the first down. That was only the fifth play the Bears had run on the 49ers’ side of the field in the half.

The Bears finally challenged the 49ers deep, running a double move (out and up) with Alshon Jeffery that drew an illegal contact call. Two plays later, Cutler endured a vicious hit from Quinton Dial that drew a roughing the passer call.

Cutler, as he’s done throughout his career with the Bears, picked himself up off the turf and picked his team up in the process. Three plays later, Cutler found his most trusted target, Brandon Marshall, who made a sparkling, one-handed catch in the end zone with 18 seconds remaining in the first half to both get the Bears on the board and build some momentum heading into the second half.

On the opening drive of the second half, the Bears defense bent but didn’t break on a 14-play, 84-yard drive, holding the 49ers to a field goal to keep it a two-possession game. During this drive, the Bears lost cornerback Charles Tillman to a right triceps injury, which is the same injury that ended his 2013 season. More medical information is needed, but judging by Tillman’s tearful reaction on the sidelines, it doesn’t look good for the 12-year veteran.

Alas, football is a violent game and injuries happen across the league. It’s a next-man-up mentality, and the Bears reserves certainly stepped up to the challenge.

The Bears were unable to get anything going with their run game, but their game plan in the second half unfolded. Coach Marc Trestman began to dial up plays using the healthier receivers from the slot to clear out and occupy the safeties over the top, as Jeffery and Marshall used their size on the perimeter to shield defenders from the ball on comeback routes and curls.

On their first drive of the second half, the Bears again went to their up-tempo attack and capitalized on an overaggressive and undisciplined 49ers defense that committed three penalties on that drive — two on third down — to keep Chicago in business.

For the second time, Cutler found Marshall in the end zone on a back-shoulder fade off of a switched release to cut the lead to 20-14.

Perhaps 49ers head coach Jim Harbaugh is stubborn, perhaps he saw an opportunity to pick on rookie Kyle Fuller, but his decision to throw the ball on first down nursing a six-point lead in the fourth quarter backfired. Fuller played the the upfield shoulder of wide receiver Michael Crabtree and was able to knife the ball out on an interception that he returned 20 yards.

Once again, the 49ers were unable to keep their head, compounding an already negative play when quarterback Colin Kaepernick picked up an unsportsmanlike conduct penalty, giving the Bears the ball first-and-goal at the 3-yard line. On the next play, Cutler found tight end Martellus Bennett singled up on the backside with a safety for an easy pitch-and-catch fade to give the Bears their first lead of the game at 21-20.

Fuller’s big night wasn’t over, as he again intercepted Kaepernick on the next drive. Showing savvy beyond his years, Fuller dropped into his underneath zone on a Cover-2 look, read Kaepernick’s eyes, then broke to the deep half to intercept a pass intended for tight end Derek Carrier. Instincts and playmaking skills on the ball is what attracted the Bears to Fuller in the first round this past May, and they were on display against the 49ers.

For the third time, Cutler connected with Marshall, this time giving the Bears a 28-20 lead that they wouldn’t relinquish in an improbable comeback.

General manager Phil Emery deserves some credit for Sunday night’s game. At one point down the stretch, the Bears had eight new defensive players on the field, four of who were rookies. Players who Emery targeted in free agency to bolster the defense (defensive ends Willie Young and Jared Allen) and the draft (Fuller and defensive tackle Will Sutton) made impact plays.

Through two games, Young has been the Bears’ best defensive player, showing burst to close on the quarterback and a strength to hold the point against the run. On the season, Young has three sacks and has earned the right to be on the field more. Allen rebounded from a quiet performance against the Bills to record three solo tackles, one tackle for loss and a forced fumble. Fuller ended the night with two interceptions.

There are certainly areas for the Bears to clean up, in particular their run blocking and on special teams, where the return game is struggling to generate field position, but overall this is a game to build on. Chicago held a potent offense to 20 points on the road, and the pass rush came to life.

When the 2014 schedule came out, Bears fans around the country penciled in their projected wins and losses for the season. Most likely, the vast majority had them at 1-1 after two games, but they didn’t expect the outcome to come this way. After two games, this team still has questions, but you can’t question their effort. The Bears played with an edge and persevered Sunday night. Qualities like that combined with top-end talent can carry a team.

Buckle up, Bears fans, because 2014 is going to be a wild ride.

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