WESTERN Bulldogs midfielder Mitch Wallis has been ruled out for the rest of the season after being diagnosed with a broken foot that will require surgery. 

The 21-year-old suffered the injury late in the third quarter of the Dogs' narrow loss to Essendon at Etihad Stadium on Sunday evening.

Wallis had limited Bombers star Dyson Heppell to 14 possessions before he hobbled from the field.

Heppell then broke free in the final term as Essendon came from behind to score a crucial victory.

Scans have revealed that Wallis suffered a break in the fifth metatarsal bone in his foot.

"People were thinking it was his ankle, but it was his foot that got twisted underneath him," sports injury expert Dr Peter Larkins told 3AW on Monday night. 

"The really nasty break that occurs on the fifth metatarsal always requires surgery … because it's got a terrible history of not healing. 

"So it's a really bad break for Mitch Wallis in terms of the location. 

"The healing time of those is quite extended. It's six to 12 weeks." 

Wallis has played 13 games in 2014 and has averaged 16.5 disposals and 4.4 tackles per match.