The Cardiac Chicago Cubs never left. They resurface every now and again, and Monday was one of those nights. But this time around, they couldn't quite get the job done. An 8-6 series-opening loss to the Detroit Tigers (47-53) was the result of a late-inning rollercoaster culminating in a three-run top of the 10th for Detroit. Missed clutch opportunities and some bad luck along the way meant the Cubs (56-44) couldn't grab what would have been their MLB-leading 11th walk-off win of the season.Here are three things we learned in the heartbreaker: A Brand New GameJun 4, 2026; Chicago, Illinois, USA; Chicago Cubs left fielder Ian Happ (8) celebrates with third baseman Alex Bregman (3) after hitting a two run home run during the seventh inning against the Oakland Athletics at Wrigley Field. Mandatory Credit: Matt Marton-Imagn Images | IMAGN IMAGES via Reuters ConnectIt was the 8th inning, and the Cubs' bats played catch-up for the entirety of the game. Seiya Suzuki and Michael Busch did their part to cut into a 4-0 deficit, their back-to-back home runs in the 3rd making it 4-3 for a good chunk of the middle innings. It wasn't until the 8th that a game that seemed way out of reach became winnable. Leave it to Ian Happ, who entered the game just 3 for his last 18, to be the one to make it happen (no pun intended). — Chicago Cubs (@Cubs) July 21, 2026Happ crushed a center-cut fastball from Tigers reliever Ryan Finnegan, going 104.8 mph off his bat and landing some 432 feet away in the right-center bleachers. Suddenly, it was tied, and Happ's 18th long ball of the season moved him up to 11th all-time in Cubs franchise history. The Cubs seemed well on their way to another walk-off win — all they needed to do was execute in the clutch.The Nail in the CoffinJun 9, 2026; Denver, Colorado, USA; Chicago Cubs third baseman Alex Bregman (3) before the game against the Colorado Rockies at Coors Field. Mandatory Credit: Ron Chenoy-Imagn Images | IMAGN IMAGES via Reuters ConnectThe Cubs had the perfect situation brewing for them in the bottom of the 9th inning. It looked a lot like how some of their previous walk-offs came to be: taking pesky at-bats, putting guys on base, and then forcing the pitcher to either pepper the strike zone or avoid it completely. Dansby Swanson began the frame by smoking a leadoff double. Michael Conforto flew out to deep center, allowing Swanson to move 90 feet from scoring the winning run. The Tigers put Pete Crow-Armstrong on base, wanting nothing to do with him.That left it up to Suzuki, Busch and Alex Bregman to bring it home. Suzuki worked a 3-1 count against Kenley Jansen. But Jansen came right back at him, getting Suzuki to chase on two consecutive pitches — the last one well out of the zone. Busch took a six-pitch walk. It was in Bregman's hands now. It should have been the end. Bregman was up 3-0 on Jansen, and all he needed to do was force one more mistake. But Bregman made it too easy for Jansen, just like Suzuki. Jansen got the count back to full before getting Bregman on a foul tip up and in on his hands — a pitch that also would have been ball four. Just like that, the Cubs' golden opportunity came undone, and the game was all but lost from there. Oh No, JamoJun 7, 2026; Chicago, Illinois, USA; Chicago Cubs starting pitcher Jameson Taillon (50) delivers a pitch against the San Francisco Giants during the first inning at Wrigley Field. Mandatory Credit: Kamil Krzaczynski-Imagn Images | IMAGN IMAGES via Reuters ConnectJameson Taillon made his return to the mound for the Cubs on Monday night, pitching at Wrigley Field for the first time since June 7. Taillon suffered a hamstring injury in that start against the San Francisco Giants, and a six-week IL stint followed.Taillon was already having command issues before his injury — he had allowed 20 home runs over his first 14 starts, a figure that, entering Monday, is still ninth-most in MLB even with his prolonged absence. RILEY WASTES NO TIME ‼️ pic.twitter.com/BiLgi3CDIp— Detroit Tigers (@tigers) July 21, 2026The Tigers attacked Taillon straight away. After two quick hits in the first inning, Taillon served Riley Greene a belt-high, 93.3-mph fastball. Greene launched a three-run shot to the bleachers in right-center field. The very next batter was Dillon Dingler, who hammered a 3-2 sinker into left to make it 4-0 very early. Taillon was able to relatively settle in after that first frame, striking out six over his 4.1 innings of work. His night was done after four earned runs on five hits with two walks. However, the damage was already done as the Cubs struggled to make up that original deficit. Taillon is carrying a 5.38 ERA over 72 innings pitched this season, and the Cubs' starting rotation has an MLB 11th-worst 4.42 ERA.Coming Up NextGame 2 of the series will feature lefty David Peterson (4-7, 6.45 ERA) on the mound for the Cubs. Peterson pitched five strong innings of two-hit, one-run ball his last time out against the Baltimore Orioles. Southpaw Framber Valdez (5-6, 4.10 ERA) is slated to get the ball for Detroit. The first pitch is scheduled for 7:05 p.m. CT. Sign up for our free newsletter to stay up-to-date with all things Chicago Cubs.Add us as a preferred source on GoogleFollow