I'm a bit confused by some parts of this. At some points, they seem to imply that at some point a team gets worse by adding more talent. For example, the title

I'm a bit confused by some parts of this. At some points, they seem to imply that at some point a team gets worse by adding more talent. For example, the title seems to be pointing in this direction. But at another point they say >its performance would begin to suffer, with fewer wins than would be expected, given the caliber of its talent. Particularly "fewer wins than would be expected" implies that while the marginal returns of top talent decrease, they don't necessarily go negative. I presume the actual paper by the researchers would clarify, but I'm not concerned enough to hunt it down.