Per the Associated Press (via ESPN FC), Kaka suffered a thigh injury while training with MLS club Orlando City, and Selecao coach Dunga has opted to bring in Firmino, 24, as the veteran forward's replacement.
The Uruguay clash is scheduled for March 26, with the match against Paraguay to be played three days later, as Brazil look to add to their tally of seven points from four matches in CONMEBOL qualifying.
Firmino is undoubtedly deserving of a call-up following an excellent start to 2016 for Liverpool, per the club's Twitter feed:
His latest goal came against Crystal Palace on Sunday, when 10-man Liverpool came back from 1-0 down to win 2-1 in the Premier League.
Per Goal.com's Dejan Kalinic, the former Hoffenheim star has earned 11 caps with Brazil, last netting for his country against Venezuela in the 2015 Copa America.