The 35-year-old Argentine guard turned back the clock with a 24-point performance as San Antonio beat the Miami Heat 114-104 and took a 3-2 lead over the defending champions in the best-of-seven series.
"I really didn't expect a 24-point game. It didn't happen all season long," Ginobli told reporters. "But I needed to feel more important, more of a threat attacking the rim, and good to see it happen."
Following his team's Game Four 109-93 loss on Thursday in which he shot 1-for-5, the three-time NBA champion said he was pondering retirement after a season where injuries have taken a toll.
Ginobli averaged 7.5 points over the first four games of the Finals and his 38 percent playoff shooting percentage heading into Sunday's game was a career worst.
On Sunday Ginobli had the AT&T Center crowd chanting his name during a game in which he went 8-of-14 from the field and added a team-high 10 assists.
"He's come to practice and worked on his shot. He's seen film. He has confidence in himself that he should just continue to compete," said Spurs head coach Gregg Popovich.
"That's what he's done his whole career. And tonight he played his best game in a while."
He was instrumental during a dazzling stretch that spanned the third and fourth quarters, scoring 11 points as the Spurs built a game-high 20-point lead with nine minutes to play.
His performance could not have come at a more opportune time for the Spurs, who head to Miami needing to win one of the next two games for their first championship since winning a fourth NBA title in 2007.
There were questions as to whether Ginobli, a two-time All-Star who has spent his entire career with the Spurs, would even be in the team's starting lineup for the pivotal Game Five. He found out he would start ahead of Saturday's practice.
"I told you Manu was going to play good. You didn't believe me," Parker said before the gathered media could ask the opening question of his post-game news conference.
"Everybody was behind him. I defended him the whole time. I was feeling a big game for Manu. I've been playing with him for a long time.
"I said this morning 'it's a great opportunity for Manu'."