A Boston Celtics executive admits losing All-Star big man Al Horford to the Phiadelphia 76ers was “huge.”

Horford signed a four-year, $109 million deal with the Sixers in free agency after declining his $30.1 million player option with the Celtics.

This particular exec says the Celtics didn't feel comfortable matching the offer Horford got from the Sixers.

“Huge. I mean what else could I say? He and Marcus (Smart) did everything for us defensively. It’s a big loss on that end,” the team executive told Keith Smith of Celtics Blog. “We wanted to keep him. Thought we would keep him. But he got an offer we weren’t comfortable with trying to match. It’s hard to lose Al, especially in the division, but building a roster is about this year and all the other years after.

“We were ready to make a bunch of moves to allow us to re-sign Al, but that number wasn’t a number we could do.”

Al Horford averaged 13.6 points, 6.7 rebounds and 4.2 assists in 2018-19 while shooting 53.5 percent from the field, 36.0 percent from beyond the arc and 82.1 percent from the free-throw line.

The Celtics signed Enes Kanter as Horford's replacement. Kanter is a solid scorer and rebounder, but he doesn't impact the game on the defensive end of the floor like Horford does. Boston is going to miss Horford on both sides of the ball tremendously.