Wuertz was 1-1 with a 3.63 earned run average in 45 relief appearances for the Cubs last season. He also spent part of the campaign at Triple-A Iowa and posted a mark of 0-1 with a 3.60 ERA and four saves in 17 games.
The 30-year-old right-hander has compiled a record of 13-7 with one save and a 3.57 ERA in 265 relief outings over five seasons with the Cubs. He has 270 strikeouts in 262 1/3 lifetime innings.
Robnett, a first-round pick by the Athletics in 2004, played at three different levels last season. The outfielder hit .240 with four homers and 27 RBI in 82 games for Single-A Stockton, Double-A Midland and Triple-A Sacramento in 2008.
Sellers, an infielder, spent the 2008 campaign at Midland and batted .255 with six homers and 46 RBI in 123 games.