— When the season began, almost all the questions about South Carolina’s starting pitching rotation involved fifth-year senior left-hander Nolan Belcher, who had not started consistently since 2009 and missed 2011 because of Tommy John surgery.

Nobody really wondered what the Gamecocks might get from Colby Holmes, the senior righty who was a weekend starter the past two seasons and entered this year with 35 career starts. After all, his earned run average had dropped every year of his career — from 5.33 to 3.69 to 3.05 last year. The past two seasons, he had 142 strikeouts and 38 walks.

Yes, Holmes must locate his pitches well because his stuff, as baseball people call it, is not overpowering. And sure, he struggled in his College World Series starts last season.

But Holmes was a proven commodity, certainly more so than Belcher.

While the season is still young for the Gamecocks (18-6, 2-4 Southeastern Conference), their star arm has been Belcher. Holmes has been a disaster lately, and freshman lefty Jack Wynkoop got his spot for last weekend’s series against Arkansas, which swept the Gamecocks.

Through six starts, Belcher has a 1.45 ERA, 42 strikeouts and a walk in 431/3 innings — some of the most astounding numbers in college baseball at this point.

Holmes’ five starts have comprised just 222/3 innings, and he has a 5.16 ERA, 17 strikeouts and 11 walks. He lacked control in his past three starts, during which he allowed 11 earned runs in 101/3 innings. USC lost two of those starts, to Clemson and Missouri.

Tonight at the College of Charleston, Holmes will make his first start since March 16 at Missouri. This is the first of two meetings this season between USC and Charleston, which visits Columbia on April 16. The Cougars (13-10, 4-4 Southern Conference) won their home game last season with USC — their first victory over the Gamecocks since 2007.

The Cougars will start freshman righty Nathan Helvey, who has a 3.42 ERA in five starts. This will be a good test for Helvey and a chance for USC to bolster its offense before this weekend’s Thursday-to-Saturday home series against Texas A&M. USC is hitting .172 against the SEC and .303 against non-league teams.

“The problem is that we’ll send out a guy who might not be quite ready to be a weekend starter,” said Charleston coach Monte Lee, a USC assistant from 2003-08. “And South Carolina will have a guy on the mound that could easily be a Friday or Saturday starter in our league.”

To combat the speed in USC’s batting order, Lee said the Cougars might have to throw more fastballs in order to keep the Gamecocks honest on the base paths. Even if the Gamecocks hit Helvey and hang runs on the Cougars, that means precious little for their ability to handle SEC pitching, which they must do more capably in their final 24 league games. But USC coach Chad Holbrook would love to enter the Texas A&M series feeling better about his bats.

“It’s a long, long season,” he said. “Momentum can carry you. I think our guys know that.”

Still, the most significant storyline tonight is Holmes, who can ill afford to get shelled again. USC’s ace, sophomore lefty Jordan Montgomery, could be ready to return next weekend at Tennessee from a bone stress reaction in his elbow. If Montgomery isn’t back then, Holbrook expects him to definitely return for the next series, April 11-13 at Florida. Texas A&M will be his fourth consecutive missed start.

Montgomery’s return and Belcher’s success will leave the rotation’s third spot up for grabs between Holmes, Wynkoop and sophomore righty Evan Beal, who performed well as a setup reliever before Montgomery’s injury forced him to start.

Throwing on four days of rest, Wynkoop made his first SEC start Sunday and allowed three runs in 42/3 innings — a solid but not spectacular outing. Beal shined against Missouri (one run and 10 strikeouts in 61/3 innings) but looked terrible against Arkansas (eight runs in 32/3 innings).

With Holmes starting tonight, Holbrook almost certainly will start Beal, Belcher and Wynkoop, in that order, for the second straight series, against Texas A&M. But a strong start by Holmes tonight could convince Holbrook that Holmes can again be the pitcher who nobody questioned before the season.