A little digging shows this will be the 5th time Illinois will face Northwestern looking for it's 6th win in the final week the season since 2000 (00, 08, 14, 15). Illinois is 1-3 in those games.
In 2000 and 2015, Northwestern was pretty clearly the better team heading into the games so the results were no surprise. 2000 Northwestern was the co-Big Ten champs and they won 10 games in 2015. 2008 was more of a toss up, but that was a disappointing Illini team despite being more talented. NU had 8 wins compared to our 5 heading into the matchup that season, so again, not much of a surprise that they won.
This season's matchup is the closest to 2014 when both teams were 5-6 and needing a win to make a bowl and that's the game we won fairly comfortably! This will also likely be the first time we are favored in this scenario against NU. That Northwestern team was probably better than this year's NU team and I think this year's Illini would beat the 2014 Illini handily.
I shouldn't say handily, we don't beat anyone handily, but the 2023 Illini would win on a last minute field goal.
None of this should factor into thoughts about the game on Saturday, but it should be noted that despite being 1-3, it's not like these were games where the Illini blew it against Northwestern teams they were clearly better than.