Lannan tries for a fourth consecutive victory over the NL West-leading Diamondbacks, who hope another casually late arrival to the ballpark will result in a third straight win over the Nationals on Thursday night.
After extending its winning streak to seven with a 3-2 victory over Philadelphia to open this 10-game trip, Arizona (71-59) dropped a season-high six straight to the Phillies, Atlanta and Washington (62-66) before beating the Nationals 2-0 on Tuesday.
In an attempt to relax the Diamondbacks, manager Kirk Gibson decided the team would show up later than usual and skip batting practice for that game. Arizona followed the same protocol Wednesday and it resulted in a 4-2 win.
"We've got to keep the superstition going, you know? And this is a game with a lot of superstition," said All-Star catcher Miguel Montero, who had two RBIs.
Arizona scored its most runs of the trip after totaling 12 in the previous eight games.
It will be interesting to see if the Diamondbacks' casual approach will make a difference against Lannan (8-9, 3.61 ERA), who is 3-1 with a 1.04 ERA versus Arizona.
The only two runs the left-hander gave up in his last three starts against the Diamondbacks came over seven innings of a 4-2 home win last August.
Lannan is 0-2 in his last three starts despite posting a 3.21 ERA, as eight of the 13 runs he's allowed have been unearned. Three of the five runs he yielded in five innings of Saturday's 5-0 loss to the Phillies were earned.
Montero, 4 for 12 with three RBIs in his last four games, is 0 for 3 versus Lannan.
The Diamondbacks hope Wade Miley's second career start goes better than his debut, when the left-hander allowed five runs in four innings of an 8-1 loss at Atlanta on Saturday.
"I wish I could have had a better outcome, but it was an awesome experience," said Miley, who was called up to replace the injured Jason Marquis. "I have to put it behind me, work on some things and then move on."
Washington's Ryan Zimmerman had his streak of reaching base end at 29 games after going 0 for 4 on Wednesday. Zimmerman has hit .388 with 15 RBIs in his last 30 games but is 2 for 12 with four strikeouts in the series.
Washington avoided being shut out for the third time in five games when Laynce Nix and Jonny Gomes hit back-to-back homers in the ninth Wednesday. The offensive struggles could continue if Jayson Werth misses a second straight game with a strained groin.
Werth is batting just .232 with 15 homers and 48 RBIs, but he was hitting .360 (9 for 25) in six games before getting hurt Tuesday.
"He would play if we were in a pennant race or something, but there's no sense," manager Davey Johnson told the Nationals' official website.