WHIPPANY, N.J. — Bobby Wood still refuses to say whether he was playing with an injured knee last spring.

Enjoying a breakout first season in the Bundesliga, the 24-year-old American forward missed a pair of World Cup qualifiers in March because of a back injury, then didn’t score in Hamburg’s final nine games. German media reported he had hurt a knee, and Hamburg coach Markus Gisdol said in May: “He’s trained for weeks on painkillers. He plays on painkillers.”

Wood didn’t look sharp when he returned to the U.S. national team for qualifiers in June, but scored twice in Hamburg’s opening three games of the new season.

“He’s back at full speed and ready to go,” American coach Bruce Arena said Wednesday, two days before World Cup qualifying resumes with a match against Costa Rica at nearby Red Bull Arena.

Wood is among five forwards in camp, joined by Jozy Altidore, Clint Dempsey, Jordan Morris and Chris Wondolowski.

“He has more pace than me, probably covers more distance in the game,” Dempsey said. “A physical player — challenges everything. Runs down lost causes and is good in front of goal. So he’s a player that I see continue to do well for many years.”

Born in Hawaii, Wood joined 1860 Munich’s youth academy in 2007 and made his professional debut with the club in a second-division match four years later. He was loaned to second-division Erzgebirge Aue for the second half of the 2014-15 season, then signed with another second-division team, Union Berlin, in July 2015.

He scored 17 goals in 31 league games in 2015-16, earning a contract with Hamburg. He had five goals and set up two more in 28 games in his first Bundesliga season.

But he didn’t score after March 12 and was given poor ratings by German media. Asked about the knee Wednesday, Wood said: “Yeah, I guess it was a little bit of a problem” and then chuckled.

“It certainly slowed him down a little bit,” Arena said.

Wood made his national team debut in August 2013 and scored his first goal two years later, a 90th-minute strike that gave the U.S. a 2-1 exhibition win at the Netherlands. He has eight goals in 32 international appearances, starting alongside Altidore for the first two games of the hexagonal last November, a 2-1 home loss to Mexico in which he scored the American goal, and a 4-0 debacle at Costa Rica that caused the U.S. Soccer Federation to fire Jurgen Klinsmann and bring back Arena, the U.S. coach from 1998-2006.

“We’ve got to take that loss as a learning session and kind of know you can’t just go out there and play,” Wood said. “You’ve got to mentally be ready for a very tough Costa Rican team.”

When qualifying resumed in June, Arena used Wood as an 83rd-minute substitute for a 2-0 home win over Trinidad and Tobago and started him as the lone forward three days later in a 1-1 draw at Mexico.

Arena compliments “his pace, his quick, sharp little running behind back lines, his aggressiveness.”

“He’s a guy that you need to focus on for 90 minutes,” Arena said. “He’s very active in his movement. He’s goal dangerous.”

The U.S. has moved up in the standings since Arena took over, winning two home games and drawing twice on the road. If the Americans win at home this week and get at least a tie on Tuesday at Honduras, they would head into the round’s final games in October on track for an eighth straight World Cup appearance.

Wood and Hamburg played under pressure last May. The club has never been relegated but was in danger of the drop until a 2-1 win over Wolfsburg on the season’s final day.

After the season, Hamburg gave Wood a new contract until 2021. He scored against third-tier Osnabrueck in the German Cup, then got his team’s second goal in a 3-1 win at Cologne on Friday that gave Hamburg a 2-0 Bundesliga start. Wood isn’t looking ahead just yet to a stress-free club season.

“Doesn’t keep you in the league winning two times,” he said. “It’s only six points.”