In the weeks after suffering his gruesome ankle injury on Oct. 17, Celtics forward Gordon Hayward would often sit in his basement and watch on television as his teammates played without him. It was difficult for him to watch, so he shifted his focus toward the teammates he had spent less than one regular-season game with.

Early in the year Hayward saw how rookie Daniel Theis’s playing time was fluctuating and knew it might be a challenge for him since coming here from Germany. Hayward and Theis had begun to form a bond during training camp, and now Hayward could see that his new friend could use some advice.

“He’s basically taking a pay cut to not be the best player on his team in Germany, and come over here and sit on the bench,’’ Hayward said recently. “So I’ve just like said to him, ‘Dude you’re playing extremely well when you get in. Make sure you’re always ready. Be patient. Everybody goes through this. I didn’t play at all until the end of the year my rookie season. Just stay with it.’’’

For Theis, it has been heartwarming and humbling to have the support and guidance of one of the best basketball players in the world. In turn, he has tried to help Hayward cope with the grim reality that he might not play this season.

Theis was one of the first Celtics to visit Hayward at his Wellesley home after his ankle surgery. Sometimes they would watch basketball together, and other times they would make an effort to talk about anything else.

“I try to help him, too, because he’s in a hard situation,’’ Theis said. “Just spend time with him. So I think it helps his situation and also mine. And he sees things from outside the court more than other people might, so it’s nice that he has a different view.’’

For Theis, it has been a challenge to adjust to the NBA while also getting acclimated to a new country. He has sent text messages to Celtics director of player personnel Austin Ainge, asking if it is legal to turn right at red lights here, and asking him to identify the trash compactor in his Needham home.

It is a new world for Theis, his wife, Lena, and their 2-year-old daughter, Laila, but their connection to the Hayward family has helped considerably. Lena and Hayward’s wife, Robyn, go to the gym together twice a week. The Haywards have two young daughters, too, so the families have organized play dates, sometimes along with center Aron Baynes’s family.

“The kids are all so little, and they just run around and play,’’ Hayward said, “and literally in 30 seconds they can be best friends, and then they take their toys and like hate that person and are crying and sad, and then they’re best friends again.’’

The two families watch movies and play cards and go out to eat. It’s given Theis a bond he was not sure he would form here, at least not so soon.

“It’s helped a lot,’’ Theis said. “I came here and basically didn’t know anybody, and then I found Gordon’s family. From the beginning, we tried to find a connection. It’s nice to find a family so quick that you can spend time with instead of just sitting at home by yourself.’’

Theis, who was mostly unknown around the NBA when he signed with the Celtics last summer, has developed a valuable role for Boston. He is averaging 4.8 points and 4.2 rebounds while shooting a team-best 52 percent from the field.

When he has poor games, or when he does not play at all, he usually receives an encouraging text or call from Hayward. Hayward played for Celtics coach Brad Stevens at Butler and knows him as well as anyone. He knows that sometimes Stevens will keep a player on the bench because of a matchup, and then call his number the next night. He wanted Theis to understand this, too.

“Sometimes I just talk to him a little bit that we need his 7 or 8 minutes some games, and they’re still just as important as Kyrie [Irving’s] 40 minutes.,’’ Hayward said. “And he’s been good about it. He’s been really good.’’

Theis said that Hayward was quite discouraged in the days after his injury. But he said once Hayward was able to get back to the practice facility and start taking shots while sitting in a chair, his mood immediately improved.

Hayward has progressed significantly since then. He has shed his ankle brace and is able to do some light spot shooting. And Theis, for one, is eager to see the next steps.

“I can’t wait to see him like when he is out doing his workouts again,’’ Theis said. “It’s been a long time. Now he’s shooting and lifting, but when he starts doing basketball stuff and movements, he’s going to be happier. And then whenever he’s back on the court for practice or playing with us, it’s going to be fun for everybody.’’

Adam Himmelsbach can be reached at adam.himmelsbach@globe.com. Follow him on Twitter @adamhimmelsbach.