If you hadn’t noticed, the White Sox are going for it. No, they haven’t officially landed Jeff Samardzija yet, but they have just completed a pretty dramatic upgrade of their bullpen.

Source confirms: #WhiteSox signing David Robertson to four-year deal for at least $40M. First reported: @bobnightengale.

— Ken Rosenthal (@Ken_Rosenthal) December 9, 2014

The White Sox bullpen was a huge problem. Overall, our forecast had the entire group being worth +0.3 WAR, the second worst collection of relievers in baseball. David Robertson immediately changes that calculation, given that he’s forecast for +1.8 WAR in 65 innings pitched. Adding Robertson to the White Sox group pushes them from something like worst in the league to middle of the pack. He’s that good.

Over the last three years, among relievers who have averaged 60 IP per season, Robertson ranks 10th in ERA-, 6th in FIP-, and 5th in xFIP-. He’s not quite Craig Kimbrel or Aroldis Chapman, but he’s comfortably in the next tier of dominant relievers. You don’t want to overpay a free agent closer just because a good reliever happened to be given the 9th inning and accrued a bunch of cheap saves, but that’s not Robertson’s resume. He’s a true relief ace.

Now, relievers are still highly volatile, and nearly every big money contract for an ace reliever has gone south in recent years. $40 million — or maybe more, given the “at least” in Rosenthal’s tweet — plus the surrendering of a second round draft choice means that Robertson isn’t coming cheap, and it’s unlikely that he’ll still be one of the game’s best relievers by the time this contract ends.

But for the next couple of years, Robertson should make the White Sox quite a bit better. And given that they’ve clearly decided to push their chips in on 2015, making short-term upgrades is probably a good plan. You don’t trade for Jeff Samardzija and surround him with the 2014 White Sox roster. If you’re going to make that kind of move, you’re also going to try and put a supporting cast in place to try and make that move worthwhile.

David Robertson is the kind of player who can help do just that. The White Sox bullpen was terrible. David Robertson makes it kind of okay. If they add Samardzija tomorrow and find a couple more position players, the White Sox could be pretty interesting next year.