The forward came on for David Villa after 66 minutes, making his first appearance since having knee surgery in April, and netted the side's fifth goal 10 minutes later.
He was the only member of Vicente del Bosque's 23-man squad who had yet to feature after warm-up wins over Saudi Arabia and South Korea in Austria.
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"I haven't played for almost two months and was very keen to return, but I wasn't as ready as I thought and had to ease off a little (last week)," Torres told Spanish state television.
"The coach and the doctors held me back a while, but in the end they gave me a run out, and I managed to score."
With a starting XI that looked much like their strongest line up Spain raced into the lead, Iniesta crossing for Villa to put away with the defender's help, as they slid in at the back post after 12 minutes.
Villa's 38th goal for Spain, which leaves him just six short of record holder Raul, rocked the Poles and they quickly conceded a fabulous second.
Iniesta was stationary and surrounded by defenders when he spotted Barcelona team mate Xavi's run into the area, and lifted the ball over the defence. Xavi squared first time for Silva who slotted away unmarked.
Alonso's long-range shot deflected in after 51 minutes, and substitute Fabregas scored with almost his first touch in the 58th after running onto an Alonso through ball.
Torres was given a rousing reception when he ran on and crowned his comeback with a goal, a first-time shot from Pedro's low cross after a trademark Spanish passing move.
Spain's opening Group H fixture is against Switzerland in Durban on June 16, before they face Honduras and then Chile.
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