Guthrie, who suffered a right shoulder injury in a bicycle accident on April 23, reported feeling fine after a bullpen session on Saturday. He played catch on Monday and will face hitters at Petco Park on Tuesday afternoon. If all goes well, Guthrie will head to the Minors, most likely Triple-A Colorado Springs.
The Rockies' Opening Day starter, Guthrie (2-1, 5.92 ERA) won his last start, when he held the Brewers to one run and three hits over seven innings in a 4-1 victory on April 22.
Manager Jim Tracy said Guthrie's session on Tuesday will be 30 pitches -- a warmup, 15 pitches, then a between-innings rest and 15 more pitches.