Boras told MLB.com that Keuchel, the 2015 AL Cy Young winner, has been throwing simulated games every five days to stay in shape. Keuchel has been throwing between 95 and 104 pitches in those outings.
Keuchel, 31, became a free agent in October. A team is required to give up a pick in next week's MLB Draft if they sign him before Sunday because the Astros gave Keuchel a qualifying offer.
Keuchel rejected the qualifying offer, which was a one-year, $17.9 million contract from the Astros in November.
Keuchel went 12-11 with a 3.74 ERA in a career-high 34 starts last year. He struck out 153 hitters in 204 1/2 innings.
The veteran left-hander only allowed four runs in 10 postseason innings. Houston lost to the Boston Red Sox in the American League Championship Series.
Keuchel is 76-63 with a 3.66 ERA in his career. The two-time All-Star had pitched his entire career for the Astros before entering free agency.