The right-hander will get his latest opportunity Monday night, when he takes the mound for his Nationals debut against the 3-0 Mets at Citi Field.
Washington is Jackson's seventh organization and fourth in the last two years. He signed a one-year deal with the club in February for $11 million after going 12-9 with a 3.79 ERA for the White Sox and Cardinals in 2011.
"For the most part, I went with what I felt would be better for me. I would be coming here for one year," said Jackson, who hopes to stay beyond 2012. "You never know, it could be more than a one-year deal. Who knows what the future holds?"
In his six previous debuts with a new team, Jackson is 3-1 with a 2.75 ERA, 30 strikeouts and 11 walks in 39 1/3 innings.
Jackson's first debut came with the Dodgers on Sept. 9, 2003, when he celebrated his 20th birthday by outdueling the D-backs' Randy Johnson with six innings of one-run ball. His most recent came with the Cardinals last July 29, when he held the Cubs to one run in seven innings.
Jackson was shaky for the Nationals during Spring Training, with a 6.51 ERA and 33 hits allowed in 27 2/3 innings.
"I have a lot of confidence in myself," Jackson said after a rough start against the Orioles on March 24. "When we start playing [in the regular season], I'll be ready to go, for sure. Of course, it's always good to be lights-out in Spring Training, but sometimes it doesn't happen like that."
Nationals: Leadoff production from Desmond
Ian Desmond's career on-base percentage barely tops .300, which is far from an ideal number for a leadoff hitter, but the shortstop posted solid back-to-back games against the Cubs this weekend.
Desmond went 3-for-5 on Saturday with a stolen base and a run scored, then followed that up Sunday by doubling as part of a 2-for-4 effort.
Still, Desmond has walked once in three games and only 69 times in more than 1,300 career plate appearances.
Mets: Pressure on for Pelfrey?
Spring Training performance typically isn't too meaningful, especially for a veteran, but it was hard to ignore the struggles of Mets righty Mike Pelfrey early in Grapefruit League play.
Pelfrey surrendered at least four earned runs in each of his first four starts and carried an 11.49 ERA. In fact, toward the end of spring, the club floated the idea of cutting Pelfrey, although the 28-year-old ultimately made the team and will start Monday against the Nationals.
He did bounce back in his final two Grapefruit League starts, giving up two earned runs in 10 1/3 innings, but the Mets still figure to watch him closely.
"I had a pretty good idea of where the ball was going to go, and I think when you get that, I think you're ready to go," Pelfrey said after his final spring outing, against the Yankees on April 3. "I feel good. I'm excited to get out of here and start the season."
Pelfrey posted a 15-9 record with a 3.66 ERA in 2010 but slipped to 7-13, 4.74 in '11, including an ERA over 5.00 in both August and September.
Manager Terry Collins has employed a platoon in center field in the two games since Andres Torres went on the disabled list with a strained left calf. Rookie left-handed hitter Kirk Nieuwenhuis was called up and started Saturday against righty Jair Jurrjens, while the right-handed-hitting Scott Hairston was in the lineup Sunday against lefty Mike Minor.
Nieuwenhuis, the Mets' third-round pick in 2008, has mainly played center field in the Minor Leagues. Hairston has made 118 of his 426 career starts in center, including eight last season with the Mets.
Nationals third baseman Ryan Zimmerman sports an OPS of only .700 in 100 career games against the Mets, easily his lowest mark against any team (minimum 10 games).
The Mets are starting their second of four consecutive series against National League East foes, as they will follow their three games against the Nationals with trips to Philadelphia and Atlanta. New York plays 15 of its first 19 contests against division rivals.