Arrieta tossed 46 pitches on Sunday with no restrictions on his right thumb after being limited to 34 pitches on Thursday because of a blister.
The 30-year-old Arrieta delivered a breakout 2015 campaign with a 22-6 record, a 1.77 ERA and a 0.86 WHIP over 33 starts and 229 innings (permitting just 150 hits). His performance guided the Cubs to the National league Championship Series, where they lost to the New York Mets.
Arrieta is set to anchor a rotation that also includes Jon Lester, John Lackey, Jason Hammel and Kyle Hendricks. Trevor Cahill is expected to serve as an emergency starter. Travis Wood, Adam Warren and Clayton Richard will open the season in the bullpen, Maddon said.