Siwelele are set to open their 2019/20 Premier Soccer League (PSL) campaign against the Buccaneers at the Orlando Stadium in Soweto on Saturday.
Seema, who is a former Pirates captain, stressed the importance of taking their goal scoring opportunities against a big team like Bucs.
"It will be a difficult match because we are facing one of the biggest teams in the PSL and on the Africa continent," Seema told Goal.
"We will give them the respect they deserve, but we are both campaigning in the PSL and we want to do well against them.
"We have to find the right balance between defending and attacking. We have to take our chances and defend well at the same time," he added.
Celtic could face their former players in Bongani Sam, Tshegofatso Mabasa and Kabelo Dlamini, who recently joined Pirates.
The trio played an instrumental role in helping Phunya Sele Sele finish eighth in the PSL last season qualify for this year's MTN8 Cup.
Seema admitted that Celtic will miss the three players, but he made it clear that he side has not been weakened as the club has signed 10 new players.
"Yes, we have lost important players, who made a huge impact for us last season. We will miss them," he admitted.
"However, we have signed 10 new players. They are here to help us achieve our goals.
"So, I do not believe we are weak without the three players," he concluded.
Celtic have signed Harris Tchilimbu, Mondli Mpoto, Tumelo Njoti, Aviwe Nyamende, Tumisho Mogakwe, Motebang Sera, Siphelele Luthuli, Sello Matjila, Andile Fikizolo as well as former Pirates goalkeeper Jackson Mabokgwane.