The reigning Brownlow medallist suffered a knee problem early into a three-stanza intra-club practice match at Essendon’s plush new training ground at Tullamarine.
It is unclear if the big ball-winning stoppages expert suffered just a nasty knock to his knee or if Watson actually damaged the joint in heavier contact.
The Bombers were playing three 20-minute terms in full macth practice.
Concerned medical staff examined the superstar on-baller and Watson was escorted from the field.
He limped from the ground and took no further part in the practice match.
Watson’s injury is reported to be on the inside of his knee with scans expected to be taken through Monday with further assessments on the mid-field gun completed late the same day.
Watson, who turns 28 on Friday, had a completely injury-free season last year with 22 outings at the Bomber’s helm and stormed to a stunning Brownlow Medal lead with 26 votes from his first 13 games of 2012.
The Bombers premier play-maker held on to win the game’s most coveted individual honour with 30 votes with only four votes from his last nine outings.
The Bombers suffered heavy losses as a soft tissue injury plague stifled Essendon’s finals push and the Bombers tumbled from a premiership threatening fourth at Round 14 to miss finals altogether down in 11th spot.