Sources: BoSox acquire lefty Miley from 'Zona for 2 starters, prospect

After losing the Jon Lester sweepstakes to the Chicago Cubs, the Boston Red Sox haven't given up on improving their rotation.

The Red Sox agreed in principle with the Arizona Diamondbacks on Wednesday to acquire left-hander Wade Miley for right-handed starters Allen Webster and Rubby De La Rosa and a minor leaguer to be named, sources have confirmed to FOX Sports MLB Insiders Ken Rosenthal and Jon Paul Morosi.

In his third full season, the 28-year-old Miley went 8-12 with a 4.34 ERA in 33 starts for Arizona this past year. He was 10-10 with a 3.55 ERA in 2013 and was 16-11 with a 3.33 ERA in 2012.

Webster, who turns 25 in February, went 5-3 with a 5.03 ERA in 11 starts last year for Boston. He was 1-2 with an 8.60 ERA in eight games (seven starts) during his debut season in 2013.

The four-year veteran De La Rosa, who turns 26 in March, posted a 4-8 record with a 4.43 ERA in 19 games (18 starts) last season.