Red Sox pitcher Allen Webster is just 23 years old. When he came up for his first start on April 21 — a no decision in a 5-4 loss to Kansas City at Fenway — he deserved just as much credit for not being unnerved by the situation as he did for earning the quality start. Since then, his three other appearances have run the gamut. He had an ugly, 12⁄3-innings home start against Minnesota in which he allowed eight earned runs in a blowout loss on May 8. After another subpar performance at Detroit on June 22, the right-hander settled down a bit vs. Toronto on June 28 at Fenway, going six innings and allowing four earned runs in a game the Red Sox won, 7-5. While experience on a big league mound can’t be rushed, it’s something Webster is growing into. It’s a learning process, and though Webster may look even younger than his age, he’s not as fresh-faced as he was at the start of the season. When Webster takes the mound today against the Padres, manager John Farrell is looking for consistency from the heralded prospect who was acquired in last year’s mega-deal with the Los Angeles Dodgers that allowed the Sox to ship out John Beckett, Carl Crawford, Adrian Gonzalez and Nick Punto. “The last couple starts we’ve seen more of a three-pitch mix and more of a willingness to use all three pitches,” Farrell said. “In the start against Minnesota, he didn’t have the luxury of getting in the flow of the game, so things kind of got out of hand early. But last outing against Toronto, when he was able to get through that first inning, putting up a zero, he got in the rhythm of the game better.