Boyd is nursing a calf injury, and has been ruled out for the next two to three weeks.
In the absence of an official leadership group this year, the club has called on the experienced Murphy to set the example.
"We've got probably six great Western Bulldogs people who can all do the role," coach Brendan McCartney told a media conference on Tuesday.
"Part of the captain's role is to toss the coin, but once the game starts, you need six to 10 leaders out there."
Even so, Boyd's injury is disappointing, on the eve of the season.
"We thought it was a cork but it didn't respond, and further investigation saw a little knick," McCartney said.
"It's unfortunate, but the game's not waiting for Matthew, and it's not waiting for injured players. Someone else gets a chance now."
In better news for the Bulldogs, Shaun Higgins is a definite starter.
"He's had a terrific summer, Shaun. The best preparation he's had for two or three years and he's set himself up for a good year," McCartney said.
Adam Cooney's pre-season was interrupted by an infection in his knee, but whether he plays this week is a simple matter.
"If he trains well, we'll play him," McCartney said.
Robert Murphy is a defender in NAB AFL Fantasy. He is valued at $360,900 in NAB AFL Fantasy Dream Team. Register your team at AFL Fantasy Hub
