Don't see how this makes sense unless he is immediately loaned back out somewhere else until the winter window. Unless Pirlo retires. In which case, your new DP is a guy most of us have never heard of.
Depth, depth, depth. Every time an MLS team plays a US Open Cup game or a CCL game, people bring up the league's lack of depth. Then when we deepen our roster, people say we have no need.
We have 10 games between now and June 3. That's one game every 4.6 days. And after that we start with US Open Cup games. Plus international breaks, including losing Herrera and Lewis to the U-20 World Cup. Add in potential injuries (all are shitty, but be happy our two big ones so far are "just" Shelton and Lopez). Add in 2-3 red card suspensions.
Compare to 2016 (italics made fewer than 10 appearances, *half season with club):
2016: Pirlo, Iraola, McNamara, Lampard, Bravo,
Mix, Lopez, Poku*, Ballouchy
2017: Pirlo, Moralez, Ring, McNamara, Camargo, Herrera, Phiri*
This year Pirlo is due for a potentially significantly reduced work load. As mentioned, Herrera won't be here due to the U-20 World Cup. Phiri wouldn't join until August. Pirlo, Ring, and Camargo are all on expiring contracts. How many more reasons can I think of?
Is it a short-term move for an urgent need? Not really, but the depth is welcome. And factoring in long term fit, it definitely makes sense, if true.