Effross, 28, is a sidearmer in the midst of a standout rookie season. In 44 innings, he has a 2.66 ERA, a strikeout-to-walk ratio of more than 4-to-1 and 2.19 FIP (fielding independent pitching), the 10th best in baseball among pitchers with more than 40 innings.
Trades for relievers with multiple years of team control has been a focus of teams at this deadline -- and in the case of Effross, he will not reach free agency until after the 2027 season. The Yankees are betting on him retaining his effectiveness, something evaluators believe he can do in spite of a fastball that sits around 90 mph.
Effross' excellent command of his fastball and slider (with a unique changeup) has allowed him to strike out 50 batters and walk just 11. His best attribute might be his ability to keep the ball in the ballpark. Effross has allowed just two home runs this year after giving up two in a 14⅔-inning stint late last season.
"He's actually been someone that has been on our radar for several months,'' Yankees manager Aaron Boone told reporters Monday. "I've heard his name a lot. I know our guys have liked him a lot and obviously he's had a really good season this year for the Cubs.''
A 15th-round pick out of the University of Indiana in the 2015 draft, Effross pitched parts of seven seasons in the Cubs' system before his debut last year. He was immediately effective last season, too, striking out 18 and walking just one.
Wesneski, 24, is 6-7 with a 3.51 ERA in 19 starts for Triple-A Scranton/Wilkes-Barre this season. The Yankees selected him in the sixth round of the 2019 draft out of Sam Houston State.
The trade of Effross came a day after the San Francisco Giants' acquisition of shortstop Dixon Machado, who had been in the Cubs' minor league system. Chicago is expected in the time before the Tuesday trade deadline at 6 p.m. ET to move catcher Willson Contreras and relievers David Robertson and Mychal Givens. Outfielder Ian Happ, who has a year of team control remaining, could be dealt as well.
The Associated Press contributed to this report.