The trade of Zach Duke a few days ago nearly marks the end of another era during the Pirates’ 18-year run of futility.

Five short years ago, Duke figured to be the beginning of a bright young starting rotation that would reverse the fate of the franchise.

It wasn’t to be.

Four years in a row, a new young starting pitcher emerged on the staff, seemingly ready to take the role as the ace of the rotation.

Duke was the first of them.

Upon receiving his call to the big leagues in 2005, he posted an 8-2 record and a 1.81 earned run average for the balance of that season.

Duke was unhittable at times, showing pinpoint control for the rest of the year.

Since that promising rookie year, Duke is 37-68 with a 4.80 earned run average. He’s allowed 443 hits over the past two years.

Now he’s a Diamondback.

Ian Snell, a hard-throwing right-hander with solid strikeout numbers, posted a 14-11 record in 2006.

Snell eventually melted down, asked for a demotion to Class AAA, reportedly considered suicide and was shipped off to the Seattle Mariners. After posting an 0-5 record and 6.41 ERA for the M’s last season, he was designated for assignment and is now a free agent.

Enter Tom Gorzelanny, who was 14-10 in 2007 as a tall left-hander with a tantalizing curveball. His star quickly faded, however.

Gorzelanny was traded to the Cubs for right-hander Kevin Hart, who has dropped off the radar himself after requiring major surgery. Gorzelanny was 7-9 with a 4.09 ERA for Chicago last season.

Finally, we come to Paul Maholm. This southpaw was 9-9 with a solid 3.71 ERA in 206 innings in 2008. It appeared he would become the highly elusive ace.

Alas, Maholm has fallen on hard times. He was 9-15 with an ERA of 5.10 in 2010.

While all of this was going on, the Pirates were drafting and trying to develop pitchers like Bobby Bradley, John Van Benschoten and Bryan Bullington.

That didn’t work out too well, either.

The moral of this tale?

Pitching is the hardest thing to develop in baseball.

Only a couple of teams can afford to buy arms, so most teams have to develop their own.

If you succeed — like the Tampa Bay Rays and San Francisco Giants — you can win.

Now the Pirates are trying it again with prospects like Brad Lincoln, Bryan Morris, Charlie Morton, Donnie Veal, Tim Alderson, Jeff Locke and Rudy Owens, not to mention the two top-flight pitching prospects they selected in 2010.

If half of these guys make it, so will the Pirates.

If they don’t, they won’t.

The Bucs have some quality young hitters. That showed last summer.

But you gotta get the other guys out.