There’s no doubt as to who has been the Arizona Diamondbacks’ best starting pitcher in 2013.

Patrick Corbin, the 24-year-old left-hander, won a job in the starting rotation in spring training, and has run with the opportunity. Corbin leads the team with 13 wins, a 2.96 ERA and represented the D-backs at the MLB All-Star Game in New York in July.

But things haven’t gone so well in Corbin’s last two starts. The lefty has gone 0-2 with an inflated ERA of 11.32 in just 10.1 innings of work in starts against Philadelphia August 25 and Sunday versus San Francisco.

Diamondbacks manager Kirk Gibson is aware of Corbin’s recent struggles, especially the ones he experienced Sunday.

“I think every pitcher within Major League Baseball goes through times when they’re not hitting their spots, maybe they don’t have the action on the pitches like they did earlier in the year or they like to have,” Gibson told Burns and Gambo on Arizona Sports 620 Tuesday. “The outing just did not go as Patrick Corbin’s outings have been going for us.”

Corbin has now pitched 182.2 innings in 2013, a figure which is nearing his career-high of 186.1 innings in 2012 with Arizona, Triple-A Reno and Double-A Mobile. So is fatigue part of the problem?

“I’m sure he’s a little fatigued,” Gibson said. “Everybody is, he’s got 183 innings or so, it’s that time of the year around baseball. Every player’s got a little baggage they’re hanging on to or they’re nicked-up a little bit, you just have to deal with it and fight through it.

“Patrick says he feels fine, and we believe him. Having said that, we’ll certainly keep an eye on him from this point on.”

The trend in baseball has been for managers to proceed with caution with young pitchers. The Washington Nationals famously rested prized right-hander Stephen Strasburg last season despite the fact they qualified for the postseason for the first time since 1981 when they were the Montreal Expos.

The New York Mets, mired 21.5 games out of first place, are getting criticism for not lightening the workload of ace Matt Harvey, who suffered a partially torn UCL in his right elbow and is out for at least the rest of this season.

Would the D-backs consider a similar move with Corbin?

“I think his next start is a big start in our evaluation of that,” Gibson stated. “If he struggles again, we’ll look at. For sure, we don’t want to hurt him.

“That’s going to be up to us to make sure we don’t let him go too far this year.”

Gibson said the possibility of completely shutting Corbin down for the remainder has not been discussed internally.

Corbin is slated to make his next start Friday at AT&T Park in San Francisco against the Giants.

Follow @Vincemarotta