The opportunities are more plentiful these days.

At-bats have become regular occurrences, with a spot in the middle of the lineup the latest development.

But Casey McGehee is well aware it could all disappear if he doesn’t hold up his end of the bargain.

“You never know what could happen a month down the road,” the Milwaukee Brewers infielder said. “For the first month of the season to now, it was two totally different scenarios. And so you never know what the next month’s going to hold.”

McGehee has gone from inconspicuous to indispensable while emerging as a key cog for the Brewers over the first half of the season.

A versatile player who battled his way onto the Opening Day roster with a huge spring training only to find playing time scarce in the early going, McGehee has blossomed to the point that he’s steadily becoming a viable National League Rookie of the Year candidate.

“I think it’s a great story,” Milwaukee manager Ken Macha said. “The guy (came) in kind of a long shot to make the team, not really the fit you’re looking for because (he is) a right-handed hitter and we had all right-handed hitters in our lineup. Then spends basically a month here and gets no at-bats, but continues to work and gets an opportunity to get out there and play and has done well.”

The 26-year-old McGehee, whom the Brewers claimed off waivers from the Cubs last October, is batting .312 with five home runs and 21 RBIs. A third baseman baseman by trade as well as the club’s emergency catcher, he’s spent most of his time at second since Rickie Weeks went down with a season-ending left wrist injury — and McGehee’s play has at least helped ease the loss.

Since Weeks’ injury, McGehee is hitting .330. All of his home runs and RBIs have also come in that span, production that’s led Macha to move McGehee into the fifth spot in the lineup of late to provide protection for first baseman and cleanup hitter Prince Fielder.

Swinging a hot bat has also earned the right-handed hitting McGehee starts at third against right-handed pitchers, matchups that had previously gone to rookie Mat Gamel, a lefty.

“I really, really have tried not to focus on the numbers, because there’s been times in the minor leagues where at this same point in the year I look up and the numbers are terrible,” McGehee said. “But you’ve just got to keep going and keep grinding and they’re going to get to wherever they are at the end of the year and once the season’s over, you can look back and the numbers will tell you what kind of year you had.”

Road blocks aplenty

McGehee returned to Chicago this weekend showing no hint of resentment toward the organization that drafted him out of Fresno State in 2003. A 10th-round pick, he put together solid but not spectacular numbers in six seasons climbing the minor league ladder.

An impressive 2008 at Class AAA Iowa (.296, 12 HRs, 92 RBIs) led to a September callup, but Chicago — with Aramis Ramirez a fixture at third and two of McGehee’s minor league teammates, Ryan Theriot and Mike Fontenot, capable of playing all over the infield — placed McGehee on waivers shortly after the season to clear a spot on its 40-man roster.

Who knew the Brewers claiming him would turn out to be such a major move?

“I loved my time there with Chicago and I’ve got nothing bad to say about them,” he said. “… But from Day One of spring training, I just felt like kind of part of the family.”

After earning a roster spot by hitting .339 with six homers and 16 RBIs in 27 spring training games, though, McGehee found his opportunities limited during the first month-and-a-half of the regular season.

The Brewers had right-handed starters at third (Bill Hall) and second (Weeks), meaning left-handed hitting Craig Counsell was the obvious top option off the bench.

Before Weeks hurt his wrist, McGehee had gotten just 16 at-bats.

“Of course, everybody here wants to play and wants to be on the field,” he said. “But, with that said, at the same time it really wasn’t tough because you understood why you weren’t playing, because we had Rickie who was out of his mind at the beginning of the year.

“He was unbelievable for us and Billy got off to a pretty good start and (Counsell) was doing a great job coming in and giving those guys a spell off the bench. So it was really like, of course you want to be playing, but at the same time you understand that why would you change something that’s working at that time?”

Hard work pays off

All the behind-the-scenes work that McGehee put in early, though, is now showing up.

He was a fixture during extra batting practice, making sure to get enough swings to maintain his mechanics — even if his timing was slightly off due to the lack of actual at-bats. He also made sure to take ground balls at both second and third.

“(He) just came out and worked,” Macha said. “Something that we talked about was he had to come out and get extra (BP) as much as he could, and he did. Every time we had extra hitting, he (came) out and did it.”

And the power McGehee displayed in spring training has returned, with all five of his homers coming over the past three weeks. None was bigger than the grand slam he hit Monday against the Mets at Miller Park, a shot over the left field wall that came a half-inning after he made a costly error by dropping a routine popup.

It brought the unassuming McGehee plenty of attention, first in the form of a curtain call and then through highlights on ESPN that showed him screaming into his helmet after the grand slam — because he was still upset with himself over the drop.

“I couldn’t bring myself to watch that,” said a grinning McGehee, who has played through a sore right knee. “Quite a few friends and family and stuff called. Most were giving me a hard time and some were congratulating me. It was a really, really weird evening.”

It was also one of the latest examples of McGehee capitalizing on the opportunity in front of him.

“Some guys kind of ride the rush a little bit,” Macha said. “They’re No. 1 draft picks, they’re athletes, they get two or three shots. Other guys (have) got to work their way into that position and hopefully they do get a chance, and when they do, they take advantage of it.”