Last week, the Detroit Lions traded away defensive tackle Akeem Spence to the Dolphins and only got themselves a conditional seventh-round pick in return. Even though he’s not a great scheme fit under Matt Patricia, the move surprised many, especially when you consider that Spence started 11 games for the Lions last year.

However, one major reason the Lions likely made the move was cap space. It’s unclear exactly how much room the Lions cleared up by moving Spence, but prior to the NFL Draft, the Lions had just over $9 million in cap space according to the NFLPA report. Now that number is at $11.6 million.

So if the Lions are clearing cap space by trading a key piece from last year’s defense, surely they intend on spending that money elsewhere. It’s been almost a full week since the Lions made the move, but they still haven’t signed anyone. What gives?

Well, there’s a very good reason that the Lions—and every other NFL team—probably won’t sign anyone significant until Wednesday. Any signings from the beginning of free agency until Tuesday will affect a team’s compensatory picks in 2019. In general, here’s how compensatory picks are doled out: If you lose more players in free agency (not including cuts or trades) than you add, you’ll get awarded more compensatory picks. There are other factors included in the formula—size of contract, for example—but that’s a pretty good rule of thumb.

So any team that signs a player before Wednesday runs the risk of lowering their draft pick compensation, and that could be the difference between having a late-round draft pick or gaining nothing at all for the Lions. As things currently stand, the Lions are projected to earn a sixth-round pick in next year’s draft according to OverTheCap.com. Adding just one player could erase that pick completely.

And because just about every other team is in a similar situation, there’s no reason the Lions need to rush things. However, it’s clear the Lions traded Spence to clear some cap room. So don’t be surprised to see the Lions add a significant player later in the week. Ricky Jean Francois? Johnathan Hankins? Dez Bryant???

We’ll have to wait and see.

[Extra note: Players that were released by other teams this offseason can be added without affecting compensatory pick compensation. For example, Hankins was cut by the Colts in March, so he could be added without affecting the Lions’ draft picks next year. However, Ricky Jean Francois’ contract expired and was not cut. Adding Francois would affect the Lions’ compensatory pick calculations next year.]