Cardinal fans shouldn't be worried about the relievers.
The bullpen has been the team's best unit all year. Ryan Helsley, JoJo Romero, and Andrew Kittredge have been reliable all year, and secondary pitchers like Matthew Liberatore, Ryan Fernandez, and John King have also been pitching well this year.
The relievers in this series pitched 8.1 innings across the three games. They allowed just two earned runs and seven hits. John King allowed an inherited runner to score, but that earned run was added to Kyle Gibson's total for the day since he allowed the runner to get on base. Cardinals relievers struck out eight batters and walked just one across the three-game series.
All of that success was had without any one of the team's "big three" throwing even one pitch. Ryan Helsley, Andrew Kittredge, and JoJo Romero didn't touch the field at any point during the series. The bullpen was able to have a ton of success without the three best relievers throwing.
All year long, Cardinal relievers have been a bright spot on the season. While you won't find the team on many relief leaderboards -- they do have the ninth-best ERA as a group in baseball -- the relief corps has been steady throughout the year. They've been placed in high-leverage situations often, and they've held the lead or kept the team in the game in these situations.
Cardinal fans don't have to worry much about the bullpen after the blowout series in Cincinnati. Reinforcements like Steven Matz and Riley O'Brien are on the horizon; the team just needs to give their relievers a chance to shine late in games.