The annual Michigan State mid-season lull: quantifying the "Tom Izzo Bermuda Triangle"

Prior to the overtime thriller over No. 5 Illinois on Saturday night, an 85-82 victory for No. 10-ranked Michigan State, the Spartans had lost two game in a row and had not played well for three-straight games. To fans, it feels like MSU does this almost every year. It is the very nature of college basketball that good teams sometimes take bad losses, such as a road loss at Minnesota. It happens. But, it is the timing of the skid that feels so familiar.

Several years ago in some the corners of MSU Spartans sports internet, someone pointed out that Michigan State's winning percentage frequently took a noticeable dip in late January and early February. This was time of year was christened as the "Tom Izzo Bermuda Triangle."

I decided to also dig into this phenomena from a few different angles. I have a good database of MSU game result and spread data back to the 2006 season. I decided to study this effect using three factors: raw win percentage, performance against the spread and performance relative to the Vegas spread expectation, also known as PAVE.

Let's start with the raw win percentage and the performance against the spread data in Figures 1 and 2.

Figure 1: Michigan State's raw win percentage for the 2006-2025 seasons as a function of time (days from the beginning of season).

Figure 1: Michigan State's performance against the final Vegas line (right panel) for the 2006-2025 seasons as a function of time (days from the beginning of season).

In these two figures, I am calculating the seven-day average of the Spartans' performance for the 2006 to the 2025 season. Over this span, Michigan State has won slightly more than 70% of its games straight up and is just over 50% against the spread. These average values are shown as the horizontal line on each graph for reference.

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