The San Francisco Giants were in need of some good news. And it came from an unlikely source — Chris Heston.

The rookie right-hander pitched six solid innings to propel the Giants to a 5-2 win over the Arizona Diamondbacks on Wednesday.

Coming into Wednesday, the Giants were unsure of the health of Jake Peavy and Brandon Belt and placed Matt Cain on the disabled list.

Heston was called up to fill in Cain’s spot. But after Peavy looked good in his bullpen session before Wednesday’s game — putting him on course to start Sunday in San Diego — it looked as if Heston’s start Wednesday would be a spot start with Ryan Vogelsong filling Cain’s spot in the rotation after Peavy’s return.

But then Heston did what he did Wednesday. He gave up two unearned runs on three hits and two walks on 91 pitches over six innings. He was the first rookie pitcher to start a game for the Giants in the opening week of the season since Matt Cain in 2006. He became the first rookie pitcher to start and win a game in Week 1 since Kurt Ainsworth in 2003.

The first unearned run was his own fault. Heston hit A.J. Pollock with a pitch in the first inning, then allowed Pollock go to third on an errant pickoff throw. Pollock scored on a groundout.

“The first inning started to unravel a little bit, kind of a little shaky there,” Heston said. “But I was able settle down and get back into it.”

In the sixth, he gave up a laser double to Paul Goldschmidt. Goldschmidt advanced to third on a pitch (which should have been caught by Hector Sanchez) and scored on a passed ball by Sanchez.

And now it looks as if Heston will start Monday in the home opener against the Rockies.

“We’re not moving him,” manager Bruce Bochy said. “We need him right now. What a shot in the arm for us.”

It is an unlikely outcome given Heston’s bumpy road to this point.

Heston was drafted in the 47th round of the 2007 MLB Amateur Draft by the Twins, out of Seminole Community College in Florida. He did not sign and remained at Seminole. He was drafted in the 29th round of the 2008 Draft by the Nationals, but passed on the Nats to attend East Carolina.

The Giants drafted him in the 12th round of the 2009 Draft, and Heston signed. His pro career got off to a bumpy start, going 1-5 in Rookie ball in 2009 and 5-13 for Class A Augusta in 2010.

But things started to come together in 2011 when he went 12-4 with 3.16 ERA for Class A San Jose. He went 9-8 with a 2.24 ERA and 1.103 WHIP for Double-A Richmond in 2012, earning an Eastern League All-Star nod.

He was added to the Giants’ 40-man roster that offseason, but success didn’t follow him to Triple-A in 2013. He went 7-6 with a 5.80 ERA in 2013 and was released in August of that year to create room on the 40-man roster.

Heston re-signed with the Giants and went 12-9 with a 3.38 ERA for Triple-A Fresno last season, earning a September call-up. He started the final game of the 2014 regular season, giving up three runs in four innings against the Rockies.

He spent the past offseason bulking up — something he said the Giants have been pushing him to do for several off seasons — and it paid off this spring. He impressed the Giants, going 1-0 with 2.40 ERA with 10 strikeouts and one walk in 15 innings.

He was set to open the Triple-A season with Sacramento when Cain’s trip to the DL prompted his call-up to face the Diamondbacks.

Where does it go from here? Well, we’ll get a better idea on Monday.