Yost is referring to the trade that sent Cespedes, a promising outfielder with the Athletics, to the Red Sox for Lester and outfielder Jonny Gomes.
By the end of the day, the Boston-Oakland blockbuster was overshadowed by an American League Central division rival's big splash.
The Tigers acquired Rays starter David Price in a three-way trade just before the non-waiver Trade Deadline passed.
"It was a nice acquisition. It's a nice pitcher to have, but that doesn't change what we're trying to do," Yost said. "Is it going to make it tougher when we face [Detroit]? Yeah, I mean, that's a pretty good rotation over there, but we like our rotation too."
Jackson Alexander is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.