Promising Western Bulldogs tall Sam Darcy will be sidelined indefinitely due to breathing problems caused by a small hole in his lung.

A father-son selection in the 2021 draft, the 19-year-old has played the first two games of the AFL season before dropping down to the VFL.

Darcy sat out Footscray's VFL match against GWS last Saturday, with the Bulldogs providing an update on his absence.

"Sam reported the onset of some shortness of breath," Bulldogs' head of medicine Chris Bell said.

"Scans confirmed that he is suffering from a small hole in the lung that has leaked some air into the space between the lung and the chest wall. This has happened spontaneously and is non-traumatic which is uncommon.

"We have consulted with specialists who expect this to heal and improve with conservative management and time.

"We will monitor Sam over the coming weeks and declare him available once he is back to full health."

Meanwhile, young forward Jamarra Ugle-Hagan and defender Tim O'Brien will need to prove their fitness for Saturday night's clash with Carlton at Marvel Stadium.

Ugle-Hagan experienced groin soreness during last Saturday night's win against GWS and will undergo a fitness test this week.

The Bulldogs will definitely be without star midfielder Adam Treloar, who strained his hamstring against the Giants and will miss at least two weeks.

At Hawthorn young gun Josh Ward will sit out this Saturday's match against Melbourne due to foot soreness.

In some positive news for the struggling Hawks, fellow youngster Jai Serong is expected to be available for selection a week after being diagnosed with pericarditis.

"He's going fantastically well, he did full training today and at the end of last week," Hawks High Performance Manager Peter Burge said.