LONDON — Was that a “Greek Freak’’ guarantee, British-style?

Giannis Antetokounmpo, the young Bucks small forward, is certain of two things: His brother Thanasis will soon be signed by the Knicks, and his club is going to beat New York again Thursday at the O2.

The loquacious Bucks forward was asked if he thought the Knicks would bring up his brother, who was drafted 51st last June but has been playing in the D-League with the Westchester Knicks after not being signed to the NBA roster.

“He’s ready,’’ Antetokounmpo said at the Bucks’ practice Wednesday at O2 Arena. “I don’t think the Knicks have to lose anything. They lose 15 [straight] now. Tomorrow is going to be 16. They don’t have anything to lose. My brother could bring energy to the team and [is] hard-working, and guys from the team can see that and take something from him.’’

The Greek Freak has a right to be confident. The Bucks already have routed the 5-35 Knicks three times this season and once in the preseason.

The Knicks have three players on 10-day deals, so roster spots should open soon. Only Langston Galloway from that group is all but certain to re-up. There’s also a possibility of Andrea Bargnani being bought out. Bargnani still is nursing a sore calf and didn’t make the trip.

Antetokounmpo is sure his brother will get a chance shortly.

“He’s going to make it,’’ Antetokounmpo said. “I think the call-up is going to be soon, hopefully soon. My brother is working hard, keeps staying focused and does what it takes to make it in the league. He’s working, effort is going to pay off.

“I thought he [would] get called up before the game. I’m a little disappointed he’s not going to play tomorrow against me.’’