Oakland A’s pitcher Esteban Loaiza isn’t very good, but sometimes it’s better to be lucky anyway. Yesterday was a banner day for the former Yankee in the good fortune department. Early in the morning while (cops say) drunkenly speeding along at 120 mph in his sports car, Loaiza was pulled over before killing himself or anyone else. In the afternoon he pitched a pretty cruddy six innings of ball against the Seattle Mariners, striking out two and giving up five runs, but he got the win anyway, and because two of the runs were unearned, he even saw his ERA drop to 6.03. Good times for him.

The win was Oakland’s seventh straight and their 10th in the last 11 games, including the recent three-game sweep of the Yankees in the Bronx. On June 2 they lost a 2-1 heartbreaker to Minnesota ace Johan Santana, leaving them 25-30 and 4.5 games behind Texas. By the end of Loaiza’s well-deserved win yesterday, they were tied for first with the Rangers at 35-31. All this came with Loaiza, ace Rich Harden, center fielder Milton Bradley, and second baseman Mark Ellis spending much of this period on the disabled list and third baseman Eric Chavez, their best player, enduring an 0-for-15 slump.

Still more curiously, the streak has come with more or less the entire lineup stinking. Sophomore Nick Swisher has been the most productive A’s hitter this season, but he’s hit only one of his 17 home runs this month, and regulars Chavez, Bobby Crosby, and Jason Kendall – theoretically the heart of the lineup – all have on-base and slugging averages around .300 for the month. Frank Thomas (who went on the DL before yesterday’s game) has been killing the ball, but given his sub-Giambian baserunning at this point in his career, he’s not all that useful unless he hits a home run.

As you’d expect, the pitching has been excellent. Dan Haren, acquired two years ago in the Mark Mulder trade, has quietly been turning in a plausible imitation of Tim Hudson circa 2002. Cohorts Joe Blanton and Kirk Saarloos have been superb, and the deep, intimidating bullpen headed up by Huston Street has been smothering opponents. Save Detroit, the A’s have allowed fewer runs than any team in the league, and there’s no reason they shouldn’t be able to keep that up even with Harden on the shelf. They just have a lot of excellent pitchers and never give the ball to a Scott Erickson-type with nothing going for him.

Since the pitching’s been good enough to drive the team back into the race in the absence of any offense, you’d think that if Chavez, Crosby, Swisher, and Bradley start hitting – and there’s no reason to think they won’t – this team should be the juggernaut many (including me) predicted before the season, and go on one of Oakland’s now-traditional summer rampages through the league.

I’m a bit skeptical that they will, though. Past Oakland teams have had some specific strengths that this one lacks, and those strengths weren’t incidental to their success.

General manager Billy Beane rightly has a reputation for treating his players like financial commodities; his general strategy has been to put most of his money in a few core players and treat the rest of the roster like a day trader treats his portfolio.

These days, Beane has a fair amount of money tied up in mediocre players like Kendall and Loaiza – so much that the team pretty much has to play them no matter how bad they are – and a lot of investment in players like Harden and Crosby, who aren’t really the equals of the players like Mulder and Miguel Tejada, whom they replaced. Without the kind of solid core he once had, and without the roster flexibility to compensate for underperformance by the core players, Beane is more or less at the mercy of the team he has.

This is especially bad because one of the things that made the last Oakland core so valuable was durability. Mulder and Tejada in particular simply didn’t get hurt, but their replacements have proved to be pretty brittle. Building around a group of players who not only aren’t great but have a tendency to miss a lot of games is a pretty dodgy proposition, and Beane hasn’t helped himself by importing the notoriously fragile likes of Thomas and Bradley to fill key roles. In the past, the A’s risk was all tied up in their most disposable players; now, both their most important players and the key members of the supporting group are the riskiest ones they have. Of all the players on the roster only Chavez and Barry Zito are good bets to consistently perform at an elite level and stay healthy for the rest of the year.

None of this is reason to dismiss the A’s; they’re on a great roll, and if Swisher, Street, and Haren all continue to do what they’re capable of, the team will not only be more than fine, but will have finally managed to successfully transition into a new generation of players. Whether they can do that, and not whether Beane is going to trade Zito for a bag of donuts, is really the primary question that will surround the A’s through the rest of the summer.

tmarchman@nysun.com