Willis was a pitching coach for the Cleveland Indians from 2003 to 2009, with his time there overlapping with current Red Sox manager John Farrell's time as the Indians' farm director. Willis later moved on to the Seattle Mariners, first as a minor-league pitching coordinator and then as major-league pitching coach, and was managing the Columbus Clippers Triple-A team up until Friday night.
"They're to announce it for me (Saturday)," Willis said. "The deal was I didn't want to leave until the Indians could arrange for someone to get here, and they're prepared to get through the weekend without somebody in Boston."
The 54-year-old Willis will join the Red Sox after Saturday's game against the Toronto Blue Jays.
The Red Sox removed Juan Nieves from the position earlier this week, citing no specific incident beyond a general lack of success for Boston's pitching staff. Boston has the worst ERA in the American League (4.95) and their ERA-FIP gap - the gap between their actual ERA and a fielding-independent pitching metric - is second only to the Indians in the AL.
That could mean Boston's pitchers are due for some natural regression, corrections that Willis may be able to help with. Buchholz, in particular, has underperformed his metrics significantly, with his 27.4-percent strikeout rate failing to save him from an unsightly 6.03 ERA. Boston's rotation as a whole ranks fourth in the AL in strikeout percentage, but walks and batting average on balls in play have done them in.
Willis took over the Mariners' pitching coach job in late 2010, and 2011 saw the staff as a whole make a significant gain in strikeouts, one that was followed the next year by a drop in ERA. His success with the Indians was more up-and-down, but in his third year on the job, Cleveland owned the best ERA in the AL.