"That had been considered," Mills said.
Lee made his 12th start at first on Tuesday against Washington -- his most extensive time at the position since five games and four starts for the White Sox in his 1999 rookie season -- and has reached a quick comfort level there.
"He's looked good down there from Day 1. The thing is, because he had come up as an infielder, that definitely has helped him with that transition," Mills said.
Strangely, Lee's name wasn't mentioned as a possible fill-in when a knee injury forced Berkman to miss the start of the season. Mills danced around a question about whether Lee could play full-time at first in 2011.
"What are the percentages? I have no answer for that question," Mills said.
The new position certainly hasn't negatively affected Lee's work at the plate. Lee entered Tuesday with hits in eight straight games, batting .394 with three homers over that span.