One big reason for this herky-jerky Nats season, for the inability to string together wins despite an outstanding top of the rotation in Max Scherzer, Stephen Strasburg and Patrick Corbin, has been the poor work at the back of the rotation by Aníbal Sánchez (0-6 with a 5.10 ERA) and Jeremy Hellickson (2-2, 6.00). To go from bad to worse, in Thursday’s 7-6 win over the New York Mets, Sánchez left in the second inning with a left hamstring strain; he’ll go on the injured list — MRI exam and prognosis to come.

Herein lies a story of what might have been if the Nats had done next-to-nothing to the back of their rotation over the winter. To make you wince, Tanner Roark and Gio Gonzalez, D.C. fan favorites now pitching in Cincinnati and Milwaukee, have started a combined 13 games with a 2.93 ERA.

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Roark and Gonzalez appear to be just what the Nats need — but gave away. They could both still be Nats, at virtually identical cost to Sánchez and Hellickson. But many of us (certainly me) were willing to see them go even though, with hindsight, we should have seen how questionable those decisions were. Yes, this is second-guessing, but with a moral to the tale.

Last season, when Strasburg was injured and went three months between wins, the Nats’ rotation desperately needed production from Roark and Gonzalez. Instead, each had a streak where he went 1-9 during the Strasburg void. Those were the worst spells either ever had as a Nat. But the goat horns stuck.

The desire to place blame is universal. The worse things go, the more intense the need to identify culprits, lay blame or just make them disappear. In baseball, if you are a good but not great player, such as Roark and Gonzalez, who has a bad season in the middle of a colossal team disappointment, such as the 82-80 flop of the highly touted 2018 Nats, then you can quickly become an endangered species.

I understand the sentiment because I shared it. When the Nats traded Roark, dumping the salary ($10 million) he’d get in arbitration and accepting an obscure minor league reliever as the only player they got back in the deal, I thought, “reasonable.” When the Nats signed Sánchez, who had just had a spiffy 2.83 ERA season with the Atlanta Braves, locking him up for two years for $19 million, the pair of moves seemed to make perfect sense taken together. The Nats had basically traded one year of team control of Roark for two years of Sánchez.

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When the Nats ignored Gonzalez, who was widely unwanted as a free agent, then signed Hellickson from the remainder bin for $1.3 million, that seemed sensible, too — better Hellickson as fifth starter than genial, unreliable Gio.

Many, including me, overlooked a key piece of analysis. Our recent memories obscure more accurate evaluations made over longer time frames. In baseball, it’s gospel (and wise) to look at a player’s past three years for a truer read, rather than just one year where recent stats or emotions can carry excess weight.

Over the past three years, Sánchez, 35, looked like a fading journeyman with a 17-26 record and dismal 4.96 ERA.

In that span, Roark, 32, looked like a solid .500 bulldog innings eater (191 per year) with a 38-36 record and a 3.89 ERA.

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Unless you were blinded by 2018 results, who would prefer Sánchez over Roark? Both have excellent attitudes, but Sánchez has had both Tommy John and labrum surgery while Roark has proven almost indestructible.

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The Hellickson vs. Gonzalez comparison over three years is just as stark. Gonzalez was 36-31 with a 3.87 ERA and seldom missed a start. Hellickson, who spent two winters unwanted, had a 25-24 record with a 4.29 ERA. And he spent much of last season hurt.

In March, both were on the open market — cheap and lonely. The Nats tagged Hellickson. In part, they wanted to leave a path for either Erick Fedde or Joe Ross to push his way into the rotation ahead of Hellickson. Gonzalez’s reputation might have made him tougher to budge. But, come on, a mistake is a mistake. You take the best player available and let things work out.

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Every stat projection had Gonzalez with a much better 2019 than Hellickson. Now Gio, making only $2 million in Milwaukee, has a 1.69 ERA in four starts.

In Cincinnati, Roark is pitching just like — Roark. Even in a bandbox home park, he is 3-2 with a 3.50 ERA in nine starts. Both Roark and Gonzalez are being asked to work slightly fewer innings per start than when they were here. It has suited them so far. But if one or both were in D.C., as fourth and fifth starters, they’d work less as well.

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Replacing Gonzalez with Hellickson is not a “near-trade” in the same sense as Roark-for-Sánchez. You’d have to be farsighted to figure in November that you’d have a Hellickson vs. Gonzalez choice available in March. But Sánchez or Roark was a conscious decision — same salary, same rotation slot.

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One mitigating circumstance contaminates Sánchez’s stats. He pitches to contact and needs reliable defense. The Nats have often stunk behind him.

“Aníbal doesn’t change regardless of the day he pitches or any day in between. He’s a guy who loves energy, loves to have fun,” Martinez said. “His record doesn’t indicate . . . he hasn’t pitched bad. He has some unfortunate [defensive] innings that cost him a lot of pitches or unnecessary big innings.”

Like everything concerning the 2019 Nats, we may come back in a couple of months and see a different world. The entire National League East has a run differential of minus-108, the worst of any division. With two humble wins, the Nats have cut the Phillies’ division lead from eight games to six in two days.

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The Nats have now matched their longest winning streak this season — two games. Until Thursday’s win, they hadn’t even done that in more than four weeks. Last year, they only had two six-game winning streaks. That’s how to go 82-80.

By this weekend against the Chicago Cubs, the Nats will be close enough to full strength that they are out of injury excuses. Then they can focus on their biggest remaining flaw — consistency. It’s a boring baseball word. But long, exciting winning streaks, the kind the Nats haven’t had in two years, are built on it.

Correction: A previous version of this column incorrectly stated the Nationals had traded for pitcher Anibal Sanchez.

For more by Thomas Boswell, visit washingtonpost.com/boswell.