8:15 p.m. ET (ESPN) | Heinz Field
In a matchup featuring two of the NFL's most storied franchises, Monday Night Football will offer a glimpse into the league's future while giving a few tested veterans another shot in the spotlight. For Justin Fields -- the contest's youngest offensive player -- Week 9 will be about overcoming an imposing pass rush (and fan base) to emerge victorious in his prime-time debut. As for Ben Roethlisberger -- the contest's oldest offensive player -- MNF will be about sustaining momentum and staying among the AFC's best. 
Here are four things to watch for Monday night when the Steelers host the Bears:
1) Rookie's first "Fields" trip to Pittsburgh. The future is now for the Bears with Fields poised to lead the offense until the end of the season. In last week's loss to the Niners, Fields became the first Bears QB to log 100 yards rushing (10 carries, 103 yards, TD) in a game since 1973 (Bobby Douglass) while throwing for 175 yards, a touchdown and a pick. This week, the promising rookie is in for another big challenge as he looks to build off his best game as a pro and notch his third career victory. Fields' mobility, whether it's been on designed runs or out of necessity, has served him well while he continues to learn to trust his arm and receiving corps. The league-leading 26 sacks he's taken, however, are a testament to how much he and his offensive line have struggled to maintain drives. The Steelers' front four has been known to make life miserable for running backs, meaning the returning David Montgomery and emerging rookie Khalil Herbert could be in for a rough night. If neither back proves effective, it'll be on Fields, who has thrown for 200-plus once in six starts, to find a way to keep the Bears in it.
2) Big Ben looking to conquer Bears for first time since 2005. A lot has changed since Roethlisberger last vanquished Chicago. One thing that hasn't, however, is his ability to do it again. The veteran QB is 0-3 (2009, 2013, 2017) against the Bears over the last 16 years. His attempt to outlast Chicago in 2021 is aided by a three-game winning streak, a run that's seen a banged-up Big Ben average a higher passer rating (102.6) than he did during a three-game losing streak (77.7) in Weeks 2-4. He's also tossed three TDs to zero interceptions over the last three after posting a 3-4 ratio during the aforementioned skid. The Steelers haven't blown any of those games wide open -- Pittsburgh's outscored its opponents, 65-49 -- but Mike Tomlin would take efficiency and the opportunity at a fourth straight win over winning by 25 a game any day. A gritty Bears secondary, which ranks 11th in allowed pass YPG but will be without vet Eddie Jackson (hamstring), could present Chase Claypool and the oft-targeted Diontae Johnson with the toughest coverage they've seen in weeks.
3) No Mack makes Bears more vulnerable to Steelers' rushing attack. For a run defense that ranks in the bottom 10 in allowed YPG (125.0), playing without Khalil Mack (foot) for a second straight week won't improve the Bears' chances of neutralizing Najee Harris. But, if it is to do so, Akiem Hicks, Robert Quinn and Roquan Smith will need to step up, much like they did when Chicago ranked among the league's best against the run in 2020. Yes, Pittsburgh ranks near the bottom of the league in rushing YPG, but that's only because the depth behind Harris is practically non-existent. Even with the heavy workload, the first-year sensation has shown he's capable of anchoring an offense as one of the few workhorses thriving in a land of committees. Entering Week 9, Harris led all rookie backs in rushing (479) and scrimmage yards (752); he's also seen an uptick in carries in each of the past five weeks, including a season-high 26 (for 91 yards) in Week 8 against Cleveland.
4) T.J. Watt and the quest for that elusive DPOY. The youngest Watt will get another chance on MNF to hold it down for the family while substantiating his latest case for Defensive Player of the Year. His journey toward that crown is off to a good start as he has accumulated 8.5 sacks (15 QB hits), 27 tackles, three forced fumbles (two recoveries) and three passes defensed in six starts (missed Week 3). Against Chicago, Watt will have to keep his head on a swivel, even with Minkah Fitzpatrick likely spending chunks of the night as a spy. But the matchup should allow him to focus primarily on wreaking havoc up front alongside fellow world-eater Cameron Heyward. On Saturday, Watt likened the Bears' offensive approach to that of their run-heavy rivals, the Browns and Ravens. No one will confuse Fields for Lamar Jackson or the Bears RBs for Cleveland's, but facing runners that can dust defenses at a moment's notice will help Watt and the Steelers better prepare for what they might face in the postseason, should they make it.
