Jansen (pelvis) is throwing a bullpen session ahead of Friday's game against the Mariners, Chris McCosky of The Detroit News reports.
Jansen was sent to the 15-day injured list May 28 with pelvic inflammation. The 38-year-old has struggled to a career-worst 4.80 ERA, 1.20 WHIP and 19:9 K:BB across 15 innings this season. If he's able to work without setbacks during bullpens and live BP sessions, Jansen could potentially avoid a rehab assignment.