Celtic won the pre-season competition after defeating AmaZulu 1-0 in the final at Ulundi Stadium on Sunday.
"Winning the tournament has reignited the winning mentality and it was great seeing players enjoying the win," Mothokoa told the club's website.
"Since Tuesday when we arrived in Durban, the atmosphere has been sublime with players taken through their paces by our astute coach and his knowledgeable technical team. Everyone sees the importance of starting well when the season begins and the commitment that has been detected even from our new signings has been great."
He added: "Our strikers, including Victor Letsoalo and Ndumiso Mabena have been banging goals even during previous friendly games and that is good for the morale of the team. The technical team will have a positive headache selecting the team for our first game of the season because all the players are performing well and are ready for the official games."
Phunya Sele Sele, who only scored 16 goals in 30 league games last season as they narrowly avoided relegation, recently captured strikers Letsoalo and Mabena from Baroka and Platinum Stars respectively.
Siwelele will be coached by Veselin Jelušic in 2017/18. The Serbian, a former Botswana and Interclube coach, penned a two-year contract with the Premiership outfit earlier this month. He took over the reins from caretaker boss Lehlohonolo Seema, who steered the side with John Maduka after the sacking of Serame Letsoaka in October last year.