The Terps used sticky defense to race to a first-half lead, but couldn't hold on as Illinois snapped Maryland's string of 13 straight non-conference wins at home with a 71-62 victory Tuesday night in the Big Ten/ACC Challenge.
The Terps were undone partly by shooting just 60 percent (15-25) on free throws. Maryland shot just 33.3 percent from the field in the second half, when it made two of 11 3-point attempts.
"We do not right now at this point know how ... to win against a good team," Turgeon said.
Terrell Stoglin led the Terps with 25 points. James Padgett had a career-high 16.
Senior Sean Mosley attempted only four shots, scoring five points.
Turgeon said Maryland's point guards Stoglin and freshman Nick Faust struggled to get Maryland into its offense in the second half.
"I think the reason Sean couldn't get enough shots is because we couldn't get into anything. Sean has to get more shots," Turgeon said.
Also having a forgettable night was Faust, who shot 2-for-11. "The poor kid, he's lost his confidence," Turgeon said.
Maryland (3-3) led 35-31 at the half. But Illinois (7-0) forced Maryland to extend its defense by shooting better in the second half.
Guard Sam Maniscalco (24 points) had nine quick points in the second half, and his 3-pointer pushed the Illini to a 59-52 lead, its biggest advantage to that point.
The lead became 61-52 before the Terps came back. A 3-pointer by Stoglin closed the deficit to 61-57. But Maryland could get no closer.
Turgeon said of Maniscalco: "The little kid killed us."
Said Maniscalco: "I'm definitely surprising people, but I'm not surprising myself."
Maryland's last previous loss to a non-league opponent at Comcast Center was to William & Mary in 2009. The Terps entered the evening 79-7 in non-conference games in the arena.
The Illini, which used a different starting lineup in each of its first three games, won its first six games by owning the boards it was plus-eight in rebounding margin before Tuesday and holding teams to 34.6 percent shooting.
"We did a better job on the defensive end in the second half," Illinois coach Bruce Weber said. "I don't think Stoglin had anything going in the second half until the last three minutes. Either he got tired or we did a better job on him, or a little bit of both."
Weber, in his ninth season, won his 200th game and is now 200-86 at the school.
Turgeon said the Terps have already improved since losing two of three games in the Puerto Rico Tip-Off. Maryland's performance in San Juan not getting back on defense, rushing shots had caused the coach to yell and stomp his feet in front of the bench.
"I feel a lot better about our team, but we still lost," Turgeon said Tuesday night.