By this point in the season, with the weather turned crisp and Nationals Park preparing to host the most meaningful baseball game in its young existence, it is difficult to remember back to February, when the Washington Nationals still sought their first winning season yet seemed to have a pitching rotation in order. On the market, with spring training two weeks off, was one last shiny object. From the outside, Edwin Jackson seemed like whipped cream on top of a sundae. The Nationals thought of him as meat and potatoes.

“We were thinking about a lot of things,” General Manager Mike Rizzo said Tuesday. “The Strasburg shutdown, the innings shortage that we thought we had. And postseason experience was one of the factors that we thought about when we made the decision.”

Wednesday afternoon, it will be Jackson — not Stephen Strasburg, not Gio Gonzalez, not Jordan Zimmermann — who takes the ball for Washington’s first postseason baseball game in 79 years. He is quite different than all the other men who count themselves part of the Nationals’ rotation. For one, his opponent is the St. Louis Cardinals, for whom he pitched a year ago not only in a National League Division Series — as he will do Wednesday — but in the World Series.

“I feel like I’m the only one with the experience in the rotation now,” Jackson said. “It’s high expectations on me. I have high expectations on myself as well.”

But Jackson, by happenstance and not choice, has become something of a pitching mercenary. It is difficult to discuss his stuff or his record without mentioning his travels. He has been traded six times, including twice in one day. He has played for seven major league teams. He ended up in St. Louis in July 2011 because he was no longer needed by the Chicago White Sox and the Cardinals needed depth in their rotation as they tried to fight their way into the postseason picture. Jackson was attractive to St. Louis then for the same reasons the Nationals, with five starting pitchers already, found him attractive this offseason.

“Great arm,” Manager Davey Johnson said. “Great stuff.”

When Jackson signed a one-year, $11 million contract on Feb. 2, the Nationals already had Strasburg, Gonzalez, Zimmermann, Ross Detwiler, John Lannan and Chien-Ming Wang as potential starters. In parts of nine major league seasons, Jackson was 60-60 with a 4.46 ERA. He could not, no matter how much he wanted, find stability in one place.

“Before I signed, you look at the team on paper, and you definitely see there’s a lot of potential, a lot of energy,” Jackson said.

From the Nationals’ perspective, they saw Jackson not just as depth, but quality depth. The plan, Rizzo reiterated Tuesday, was to limit Strasburg’s innings in his first full season back from ligament replacement surgery in his right elbow.

That meant making sure Washington had a veteran who could, as Johnson said, “eat innings.”

“We felt that we could’ve went in with Lannan as the fifth starter, but then our depth would have been much less,” Rizzo said. “When Edwin was still out there, we felt it was a good opportunity for us, a good value for us.”

There is, too, no further commitment. After a season in which he went 10-11 with a 4.03 ERA in 1892 / 3 innings, he will be a free agent again.

“At this point, I’m out to help my team win,” Jackson said. “I’m not out to prove a point to anyone. I’m not out with a chip on my shoulder.”

That could be, in part, because he has done this before. Jackson’s first three playoff appearances came in 2008 with Tampa Bay, two in the American League Championship Series and once in the World Series. Last year, he got the ball in Game 4 of the NLDS, when the Cardinals faced elimination at the hands of the Philadephia Phillies.

The first three batters — Jimmy Rollins, Chase Utley and Hunter Pence — ripped a double, a triple and a single, respectively. Jackson trailed 2-0 before he could breathe.

“You have to slow the game down,” he said. So he did. He got a double-play ball, and lasted six innings without giving up another run. He got the win to keep the Cardinals alive.

“It’s either A or B,” Jackson said. “You get it done, or you don’t.”

It is, too, a way to look at his two starts this year against St. Louis. In Washington, Jackson struck out the side in the first inning, and went on to pitch eight innings in which he allowed one unearned run, striking out 10. In St. Louis just 12 days ago, he was chased after 15 batters, nine of whom scored; he recorded just four outs.

“We saw him in two completely different ways,” Cardinals Manager Mike Matheny said.

Which way he shows up Wednesday will help determine the Nationals’ fate this postseason, not to mention Jackson’s future. How he got here, what he’s done before, what he does next — none of it matters, he said.

“At this point,” Jackson said, “it’s: What can you do now?”