Key takeaways: Cardinals 8, Cubs 4

9:32 PM UTC

CHICAGO -- The Cubs and Cardinals have one of the oldest rivalries in all of sports -- one that is filled with heroes and villains and a long list of classic games and historic moments. St. Louis rookie Joshua Báez stepped into the rivalry for the first time on Saturday and quickly added his name to the lore.

In an 8-4 loss to the Cardinals, Cubs lefty allowed three home runs to Báez, who became the first player in Major League history to launch a trio of blasts in his big league debut. It was an all-time performance that was tough for the North Siders to overcome, evening up the series at one apiece with the rubber match coming Sunday.

Here were three takeaways from Saturday’s defeat:

1. Boyd vs. Báez

Boyd had been on a tremendous run for the Cubs, pitching into the seventh inning in each of his past four turns and spinning a 2.43 ERA over his past nine outings. Chicago picked up eight wins in that run of starts for the veteran lefty, who has looked more and more like the All-Star he was for the team last year.

Báez had something to say about that on Saturday.

In the first inning, the rookie slugger -- who had 34 homers for Triple-A Memphis prior to his promotion to the big leagues -- crushed a first-pitch fastball from Boyd out to center field. Per Statcast, the blast had a 108.6 mph exit velocity and travelled a projected 449 feet.

Boyd engaged in a longer battle with Báez in the fourth inning, but the 23-year-old outfielder worked the count full and pulled a changeup from the lefty out to left field for a leadoff shot. And then in the sixth, Báez was at it again. This time, the rookie connected on a 1-0 slider from Boyd, sending it the opposite way for a two-run homer to right.

Entering the afternoon, Boyd had allowed three home runs within 112 total batters faced across his four previous starts combined. On Saturday, the lefty was chased after being charged with seven runs on five hits (four homers) in 5 1/3 innings. Blaze Jordan ended Boyd’s day with a solo shot in the sixth.

2. Conforto’s game-tying shot

Cubs outfielder has been one of the team’s most dangerous bats off the bench this season, but the same success with slugging has not manifested as much when given chances to be in the lineup. Conforto bucked that trend in Saturday’s game.

In the second inning, Cardinals starter Michael McGreevy retired the first two batters he faced before Jordan made a fielding error on a grounder off the bat of Nico Hoerner. Pedro Ramírez followed with a double, setting things up for Conforto. The veteran outfielder drilled a 2-1 four-seamer from McGreevy out to right for a game-tying, three-run blast.

That home run was Conforto’s first since he launched a pinch-hit blast against the Tigers on July 21. In the next 14 games, he hit just .171 with a .229 slugging percentage and .508 OPS in 35 at-bats, while getting some opportunities to start. Entering Saturday, Conforto had a 1.140 OPS in 34 games as a sub and a .671 OPS in 46 games as part of the starting lineup.

3. PCA hits a cold spell

Cubs center fielder has played at an elite level for the majority of this season, putting him in the thick of the debate for the National League MVP Award. Inevitably, a bit of regression was bound to find the Cubs star at some point.

In Saturday’s game, Crow-Armstrong went 0-for-4 out of the leadoff spot for the North Siders, marking his third straight game with that showing as Chicago’s tablesetter. In fact, dating back to his homer in the third inning against the Nationals on Tuesday, Crow-Armstrong has been stuck in a 1-for-21 spell for the Cubs.

One of the benefits of the incredible, extended hot streak Crow-Armstrong was on across May and into early August is that his overall numbers still hold up when a cold stretch arrives. Entering play on Saturday, the Cubs center fielder was still leading the Majors with 7.8 WAR (per Fangraphs), with Dodgers star Shohei Ohtani (6.6) next on the board.