Based on the Wyscout data for the 43 matches Klaassen played for Werder Bremen in season 19/20 & 20/21, he has:

- 86% probability that he is able to contribute to the Werder Bremen overall,
- 5% probability that he is able to contribute to the attack of Werder Bremen,
- 97% probability that he is able to contribute to the defense of Werder Bremen,
- 83% probability that he is able to contribute to the build up and transitioning of Werder Bremen.

Based on the Wyscout data for the 19/20 season Werder Bremen as a team had:

- 31% probability that the team will win or draw a match,
- 30% probability that the attack will score,
- 43% probability that the defense will concede a goal (lower is better),
- 44% probability that the build up and transitioning will create an opportunity.

Based on the Wyscout data for the 19/20 season the Bundesliga has a FBM League Strength score of 123 points. (91% correlation)

Based on the Wyscout data for the 19/20 season the Eredivisie has a FBM League Strength score of 114 points. (91% correlation)

Based on the Wyscout data for the 19/20 season Ajax has:

- 87% probability that the team will win or draw a match,
- 69% probability that the attack will score,
- 28% probability that the defense will concede a goal (lower is better),
- 53% probability that the build up and transitioning will create an opportunity.

Given that the League Strength of the Eredivisie is lower and that the club probabilities of Ajax are higher, it is a realistic idea to see Klaassen play for Ajax.

Based on the above data including minutes played, difference in league strength and difference in team strength, we calculate the following probabilities for Klaassen playing for Ajax.

- 94% probability that he is able to contribute to Ajax overall,
- 12% probability that he is able to contribute to the attack of Ajax,
- 99% probability that he is able to contribute to the defense of Ajax,
- 92% probability that he is able to contribute to the build up and transitioning of Ajax.

As you can see the performance of Klaassen will be very similar for Ajax as it was in the 19/20 season for Werder Bremen.

If we were to substitute Van de Beek for Klaassen Ajax would get the following probabilities:

- 92% probability that the team will win a match (+6%),
- 70% probability that the attack will score (+1%),
- 26% probability that the defense will concede a goal (lower is better) (-2%),
- 53% probability that the build up and transitioning will create an opportunity (+0%).

This would result in 5 additional points in the table.

To conclude: Ajax is slightly better off with Klaassen.