I think the NEW CBA has drastically cut the level of the tax-MLE it's 5M this season:
View attachment 56667
in other words, if a team uses more than 5M of their MLE, they are using the non-Tax MLE and they will be hard-capped. Since Dallas signed Seth Curry with the BAE, they would appear to only have their non-tax-MLE to use
looking at the Dallas Spotrac page,
https://www.spotrac.com/nba/dallas-mavericks/cap/
it says Dallas is at a shade under 153M with about 12.5M in margin below the tax line and an 18M margin below the hard cap apron. But I don't think the salaries of the two Dallas 1st round picks are accounted for so that would take 7.5M off of both of those margins
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as for matching, it's always a balancing act, and the advisability on match will depend on the level of annual salary compared to when Portland is after a Dame trade. If Thybulle is making 7-9M year, it's an easy match. But if he's making 13-14M year it's not