The change is great for boxers, or players in general.

Ideally your main team/character reaches level cap quickly.
And is on par with others, throughout.

But you can experiment.
If most players had a cap of 1,800 points per week.
Your catch up cap is 1,000 / 1,800 = 0.555, or 55.5% of their gearing/points, plus whatever your weekly cap is.

So if you enter the game, nine weeks into the season.
A main team guy, would have earnt 1,800 * 8 = 14,400.
Your cap 1800 plus 1000 * 8 = 8,000, or 9,800 (9,800 / 14,400 = 0.6805).
If you cap each week, plus gain the 8,000 extra points over a week or two, you're close to 70% of their gearing by week 10, having missed weeks 1-8.
That doesn't make you more effective, by any stretch, but it would make you competitive.

If you enter the game, twenty two weeks into the season.
1,800 * 22 = 39,600.
With a week off of work, to gear your new team... you could in theory have 1,800 + (1,000 * 22 = 22,000) or 23,800.
Which while not as good as 39,600, is still going to be 60.10% of their total gearing.

The earlier you enter, the better overall.
Both in terms of the 'Catch Up' points being a higher percentage of available gearing... and in getting the full 1,800 points per week thereafter instead of only credit for 55.5% of those points.
The top teams might have more than an 1800 weekly point cap, but the masses that you compete against are on that playing field.