This past Sunday against the Kansas City Chiefs was a day to forget for 49er fans.

Hotshot Chiefs quarterback Patrick Mahomes was rolling, throwing all over the 49ers defense at ease. The 49ers' first half was some of the worst football played during the Kyle Shanahan era as they went into halftime down 35-10 with slim hopes of a comeback.

The second half was another story. The 49ers came out looking like a different team, the defense was holding, and QB Jimmy Garoppolo was leading them back. They drove down the field and Garoppolo was putting them in position to score, which would have left them within one score of a tie.

49er fans watching were telling themselves, "This is why he was brought here. This is a guy who can bring back the culture of winning with the 49ers."

After being sacked on consecutive plays, Garoppolo was flushed out on third-and-goal from the 20-yard line, sprinted left towards the sideline, and then it happened.

Garoppolo cut inside towards the goal line and collapsed. He laid on the ground clutching at his left knee, and everyone feared the worst. The instant replay from behind the play only further confirmed what we were all thinking. Jimmy Garoppolo, the 49ers' franchise QB, tore his ACL, ending his season and the hopes of all 49er fans.

We must all remember, building a successful football team is a long process that will certainly have its hurdles along the way. It may be that the 49ers are faced with their biggest hurdle in only year two of the Kyle Shanahan era.

Believe it or not, there is always a bright side to things. General manager John Lynch and head coach Kyle Shanahan have turned around a team that saw four different coaches in as many years. A team that went to three straight NFC championship games only to win 16 games combined in the following three years. A team that saw one of the worst offseasons in league history in 2015, losing head coach Jim Harbaugh who led the team to a 44-19 record in his four seasons and nine starters to retirement and cuts that included All-Pro and Pro Bowl caliber players.

In Shanahan's 19th game as head coach, the 49er fans have that expectation of winning again. That alone is something to be happy about. The reason Garoppolo's injury is such a big loss is because we as fans had that expectation. Something we haven't had in a long time.

The 49ers rushing attack has been phenomenal, and it currently has the NFL's leading rusher in Matt Breida. Late round draft picks like tight end George Kittle, wide receiver Trent Taylor, and safety Adrian Colbert have all been key additions to the 49ers and were all drafted in the 5th round or later. Breida was signed as an undrafted free agent. These players aren't going anywhere.

Marquise Goodwin has evolved as an up and coming No. 1 wide receiver under Shanahan, and linebackers Reuben Foster and rookie Fred Warner have already established themselves as one of the most feared duos in the league. Not to mention DeForest Buckner is emerging as a true All-Pro talent.

The moral of this story is that the 49ers under Lynch and Shanahan have put this team in a position that is — heading towards success. They have done it faster than most thought they could and have set a foundation for years to come. They have established a culture of winning in which the players believe as well as the fans.

Yes, we all wanted it to be "our" year. We all wanted Garoppolo to be a top quarterback and take the league by storm. Unfortunately, it will have to wait.

But this isn't the end of the 49ers, and their season isn't over.

It's just a hurdle.