PHOENIX -- Even as they find themselves in the middle of a playoff race in mid-August, the Giants haven't been afraid to lean on young starters in their rotation. A pair of 24-year-olds, Shaun Anderson and Conner Menez, debuted earlier this season. On Saturday night, it was 22-year-old Logan Webb's turn.

Battling early nerves, Webb struck out seven over five strong innings and earned the win in his Major League debut as the Giants defeated the D-backs, 11-6, to extend their winning streak to three games and secure a series victory at Chase Field. San Francisco will have a chance to sweep this four-game set when it sends Madison Bumgarner to the mound in Sunday afternoon’s series finale.

• Box score

“What a nice debut,” manager Bruce Bochy said. “Just watching [Webb] this spring, he’s got a really tough mentality. That’s what you like about him. You can tell, he’s out there and he’s all business. He didn’t let that faze him.”

Webb, the Giants’ top pitching prospect and No. 5 overall, according to MLB Pipeline, gave up two runs (one earned) on five hits and walked one in the 93-pitch effort. He is the first Giants starter to earn a win in his Major League debut since Ryan Sadowski in 2009.

Webb relied primarily on his fastball, which averaged 93.6 mph and topped out at 95 mph, though he also induced five swinging strikes on his breaking ball.

Webb said he left 30 tickets for his friends and family, many of whom drove more than 11 hours from his hometown of Rocklin, Calif., to be in the stands for his debut.

“It was awesome,” Webb said. “It was just fun to be out there. I was just excited. Those first couple of pitches, I was a little nervous. Once I got that first strike, it was fun.”

Brandon Belt crushed his second career grand slam and Kevin Pillar added a career-high five hits to back Webb, who became the youngest pitcher to start a game for the Giants since a 20-year-old Bumgarner debuted in 2009.

Mired in a deep slump, Belt was dropped out of the leadoff spot Thursday, but he has begun to heat up since moving to the bottom of the order, going 5-for-14 with two home runs and eight RBIs over the first three games of this series. He finished with six RBIs Saturday, matching his career high.

A fourth-round Draft pick in 2014, Webb was added to the Giants’ 40-man roster over the offseason and impressed during his first big league camp this spring. He opened the season at Double-A Richmond, but he made only five starts before drawing an 80-game suspension after testing positive for a performance-enhancing substance.

Webb released a statement denying that he knowingly took any PEDs, and he reiterated Friday that he still isn’t sure how the substance entered his body. After his suspension was announced, Webb headed to the Giants’ Minor League complex in Scottsdale to continue throwing. He faced hitters in simulated games to stay sharp during the long layoff.

He returned from the suspension in late July, making three starts for Richmond and one for Triple-A Sacramento. Overall, he logged a 1.85 ERA over 12 Minor League appearances before receiving his first big league callup Saturday.

The D-backs inflicted their only damage against Webb in the first inning. Jarrod Dyson led off the game with a single and scored on Wilmer Flores' RBI double to put Arizona on the board. Webb rebounded by inducing a groundout from Eduardo Escobar and striking out David Peralta on a changeup, but the D-backs added another run on a throwing error by third baseman Evan Longoria.

Webb didn’t allow a run after that, gradually settling into the game and departing with a 6-2 lead.

“He stayed poised out there,” Bochy said. “He gave us five solid innings. He looked good, didn’t he? He had good stuff. Good command. A nice slider going, changeup. The kid did a nice job in this ballpark for his debut.”

It’s unclear how long Webb’s initial stint in the Majors will last, as the Giants are expecting to keep Dereck Rodríguez in the rotation and to activate Anderson off the injured list next week in Chicago. They played Saturday’s game with a three-man bench after optioning outfielder Joey Rickard to Triple-A Sacramento, but they will likely look to add another position player Sunday and will need to make a corresponding move.

Bochy said he would gather with his staff to discuss potential moves, but either way, it’s clear Webb’s first impression was a good one.

“For a kid to come up here against a tough lineup like that -- he won’t forget tonight,” Bochy said.