Sunday afternoon at Nationals Park, Lannan again demonstrated his preternatural poise. He shook off mental mistakes in the field — both from himself and his teammates — to escape jams in both the fifth and sixth innings and help the Nats to a 2-0 victory over Chicago.

Lannan (2-2) held the powerful Cubs offense — with the best batting average in the National League — scoreless through seven innings. Relievers Luis Ayala and Jon Rauch then retired six of the seven batters they faced to close out a series win for Washington (9-17).

Lilly’s words are astonishing considering Lannan started last year at Class A Potomac and is still in just his fourth year of pro ball. His meteoric rise through the organization led to six starts last summer in D.C. But he had to begin this season at AAA Columbus before an April 5 recall.

“I’m learning every day,” said Lannan, who has allowed one run in his last three starts. “I just want to keep the ball down. You leave the ball up against these guys you’re going to get hurt.”

Lannan’s command was shaky early with a walk in each of the first three innings. No harm done as the Cubs never even pushed a runner into scoring position.

In the fifth, however, Lannan committed a mental error when he forgot to cover first base on a chopper to first baseman Nick Johnson. That left the bases loaded with just one out. No problem. A simple double-play grounder to shortstop Cristian Guzman ended that rally.

“You have to forget what happened,” said Lannan, who has pitchedat least six innings in four of five starts. “The past is the past for a reason. You can’t dwell on it because then you’re not completely in the moment.”