Baltimore Orioles starter Steve Johnson delivers a pitch to the Seattle Mariners during the sixth inning of the Orioles’ 2-0 victory. (Nick Wass/ASSOCIATED PRESS)

As the Baltimore Orioles’ improbable run of success continues, as this upstart, patchwork club keeps churning out victories, the comparisons to the Orioles’ 1989 “Why Not?” season become inevitable.

On Wednesday night, in a 9-2 clubbing of the Seattle Mariners that completed a three-game sweep and extended the Orioles’ win streak to five, the similarities to 1989 became borderline ridiculous.

Exactly 23 years to the day that unheralded right-hander Dave Johnson, “The Pride of Middle River” as he was trumpeted, notched his first big league victory at Memorial Stadium for his hometown Orioles in impressive, complete-game fashion, another rookie named Johnson took to the mound.

This time it was Dave’s 24-year-old son, Kingsville’s Steve, making his second appearance for the Orioles at Camden Yards and first start as a big leaguer.

And, of course, Johnson cruised to his first win with Dad in the stands, watching and choking back his emotions, just like his own father, a Memorial Stadium usher, did 23 years ago.

As Orioles Manager Buck Showalter would say, “Really?”

Yes, really.

As for the announced crowd of 17,312, it soaked in the moment, partying like it was, well, 1989 — when the Orioles rebounded from their worst season ever to stay in the pennant hunt until the last week of the season.

On Wednesday, the fans screamed loudly when Nick Markakis and Mark Reynolds each homered, and many rose to their feet before the seventh when it was obvious Johnson was done for the night.

The Orioles (60-51) are now in a three-way tie for the top American League wild card spot and have won eight of their last 10.

From the beginning Wednesday, Johnson was in control — because of solid control. He allowed a single in the first, but otherwise struck out the side on 12 pitches — all were strikes.

In comparison, on August 8, 1989, Dave Johnson allowed a triple to the first batter he faced, Minnesota’s Al Newman, and gave up an RBI groundout to future Hall of Famer Kirby Puckett before settling down.

So the kid one-upped the dad in the first. And, in fact, Steve Johnson’s nine strikeouts were more than his dad ever had in a big-league start — though Dave Johnson, now a MASN broadcaster, did give up fewer runs and pitch longer in his first big league win.

The son had to wiggle out of a bases-loaded, one out jam in the second inning. Munenori Kawasaki made it easier with a squeeze bunt right back at Johnson for the second out and a pop-up ended the threat. He then cruised into the sixth when he served up a two-run homer to Kyle Seager.

Overall, Johnson allowed two runs on five hits while walking two and fanning nine. He threw 97 pitches, 67 for strikes.

And, fitting for this can’t-be-happening season, Johnson was supposed to start Wednesday for Class AAA Norfolk but was needed in Baltimore because Tommy Hunter, the scheduled starter, had to warm up in the bullpen during Tuesday’s 14-inning win.

Johnson, whom the Orioles acquired in the George Sherrill trade with the Dodgers in 2009 and who could have been a minor league free agent this offseason but stayed with the Orioles, got the emergency call after posting a 2.86 ERA in 19 games at Norfolk.

Johnson’s new teammates bashed former Oriole Kevin Millwood, who lasted just four innings.

Catcher Matt Wieters followed up his two-homer game Tuesday with two doubles and five RBI.

Orioles note: The team will purchase the contract of top position player prospect Manny Machaho from Class AA Bowie. Machado likely will make his first major league start in Thursday’s series opener at home against the Kansas City Royals at third base.

— Baltimore Sun