White Sox designate Downs for assignment
The White Sox announced the moves on Thursday.
The 38-year-old Downs went 0-2 with a 6.08 ERA in 38 games this season - his first with Chicago.
Surkamp was 3-4 with a 4.54 ERA in 14 games (11 starts) with Charlotte.
He is 2-3 with a 7.36 ERA in seven starts over two major-league seasons with San Francisco (2011, '13).