Bumrah acknowledged Siraj's commitment despite dealing with the physical challenge.
Despite the discomfort, Siraj returned with a couple of wickets in 23.2 overs during Australia’s first innings.
Bumrah, who starred with the ball with six scalps to his name, acknowledged his teammate’s commitment despite dealing with the physical challenge.
"We (Siraj and I) have had conversations, but this was the conversation he had with me before we came here (Brisbane). When we came here in Perth, as well as the last game, he looked in very good spirits," Bumrah told reporters after the third day’s play in Brisbane.
"He was bowling well and he has picked up a fair few of the wickets. In this game, I will give him credit that he had a little bit of a niggle, but he still kept on bowling and still helped the team because he knew if he goes inside and he doesn't bowl, then that team will go under pressure.
"So I think he has got a great attitude and he has got a fighter spirit that the team loves," he added.
Siraj appeared to be in discomfort when he clutched his hamstring after bowling the second ball of the 37th over during Australia's first innings. The physio attended to him on the field before Siraj left, with Akash Deep completing the over.
However, the 30-year-old returned on Day 2 and got rid of Australian captain Pat Cummins and Nathan Lyon.
"I personally love that as well, that he is up for a fight and he always gives it all for the team. So I think that is the biggest positive for any cricketer going forward.
"That he gives it his absolute best on the field. And even when he is not 100% fit, when he has got a niggle, he is still fighting for the team. So that is a great attitude."
Siraj has picked up five and four wickets in the first two Tests in Perth and Adelaide but he also drawn flak for his lack of control over line and length, especially during the third Test.
However, Bumrah has advised Siraj to just focus on the things he can control. "Yes, in terms of wickets and all, some days you will bowl well, the wickets will come, as I spoke to him before. And some days you will not bowl very well, but the wickets will follow. So it's all money in the bank," Bumrah said.
"That is the conversation that I have had with him. That you keep focusing on your stuff, things that you can control.
"You wanted to play Test cricket, you are doing that. Your family is really proud of you. You are doing something that not many have done before. So I think he is in a very good space.
"I don't know what else is happening. But he has got a great attitude, and that is a very big positive for us," he explained.
The visitors were 51/4 on a rain-marred third day in reply to Australia's huge first-innings total of 445.
(With PTI Inputs)