Navy’s Shwan Anderson split the American defense on this play, but the Eagles finished with an upset win. (Ricky Carioti/The Washington Post)

In October, when the Patriot League released its men’s basketball preseason poll and Navy found itself picked last for a second straight year, Coach Ed DeChellis defiantly said: “I really don’t care what other people think. We have a chance to be as good as anyone in the league.”

Almost halfway through the conference schedule, Navy players mostly have been making good on their coach’s foresight. The Midshipmen (15-6, 6-2) are in second place, on pace for a home game in the Patriot League tournament quarterfinals as a top-four seed. They also are well within reach of 20 wins for the first time since the 1999-2000 season and have designs on the program’s first NCAA tournament bid since 1998.

All of which had Navy players predictably confident heading into Wednesday night’s game against American, ranked 345th of 346 Division I teams in points per game and the losers of six in a row to open Patriot League competition. Turns out the Midshipmen were far too comfortable, with DeChellis going so far as to say his group overlooked a youthful opponent at the bottom of the standings.

The result was a 63-58 loss at Alumni Hall in which Navy performed lethargically except for the opening minutes, allowing American to shoot 9 for 23 (39 percent) from three-point range and claim a 31-25 advantage in rebounding. The Midshipmen entered as the Patriot League’s No. 1 team in three-point field goal defense and rebounding margin.

“Our guys in my opinion are not there yet in terms of maturity,” DeChellis said. Leading up to the American game, “they see a team that’s won only one game in the league. They see a team that’s won four games” overall.

Still, the Midshipmen remain just a game and a half behind Bucknell for first place. After losing the league opener to the Bison, Navy won six straight, including 69-64 over Lehigh on Jan. 20 to end an 11-game slide against the Mountain Hawks. Navy’s longest winning streak this season was seven, and its 7-2 record at the time matched the program’s best nine-game start in 30 years.

The Midshipmen forced 15 turnovers against American but managed just eight points off of them. Navy also permitted the Eagles to shoot 48 percent in the second half, a considerable disparity from its top-ranked Patriot League field goal percentage defense (.407).

Senior point guard Tillman Dunbar (Paul VI Catholic High School) led Navy with 14 points, and sophomore forward Jace Hogan added 11 points and four rebounds. Dunbar, a four-year starter, has been a central figure in the Midshipmen’s turnaround since his first season when Navy finished 8-23 and won two games in the Patriot League.

“We’ve been building this program for a while now,” Dunbar said. “Guys have been working hard year in and year out. I guess this season, kind of tired of losing, kind of being looked over, being disrespected, so every night we try to come out and prove ourselves. Tonight we didn’t get it done, but we’ll definitely be back and improve ourselves the rest of the season.”

Navy is heading into one of its most demanding stretches with three games in five days, beginning Saturday on the road against Holy Cross. On Monday, the Midshipmen will face Army in West Point, N.Y., and are scheduled to arrive back on campus in the wee hours. That leaves another short turnaround to prepare for Boston University on Wednesday at Alumni Hall.

according to DeChellis, It’s an ideal time, according to DeChellis, to remind his players not to congratulate themselves just yet.

“What have you done? You haven’t done anything,” he said. “You haven’t had a winning season. You haven’t won the Patriot League. You haven’t done anything. We’ve got to continue to work to do what we want to do. Do we have a chance to do those things? Yeah, I think we’ve got a chance, but we’ve got to stay focused.”

American (4-15, 2-6) was able to do just that down the stretch Wednesday behind Delonte Jones (Episcopal) who matched a career high with 23 points. The freshman guard also had 23 points in an ­81-73 victory over Lafayette on Jan. 20.

Jones is among seven underclassmen on a team that is averaging 72 points over its season-high two game winning streak. Previously, the Eagles had scored more than 60 points only four times, and they came into Wednesday night’s game averaging just 54.5 points per game. Following 20 wins and a berth in the NCAA tournament two seasons ago, last year American found itself in a position Navy knows all too well, settling for 17 wins before this season’s rebuild commenced.

“It’s one thing to say that you’re close and you’re getting there each game, but each game you lose, a loss is a loss,” said Mike Brennan, the Eagles’ third-year coach. “No one cares how close the games were if you’re two and whatever. It’s the same with the guys. They just get beat down a little bit.

“So to have a win, it’s like, ‘Hey, we can do this,’ especially against one of the better teams in the league now. At least we know we can compete for an entire game and come away with a win.”