Calvin Johnson and Reggie Bush have not played together as Detroit Lions yet, but the possibilities excite each of them.

The addition of Bush, who signed a four-year, $16 million deal as a free agent, was done mostly for the purpose of opening up the field for Johnson.

This has not been lost on the man better known as Megatron. He knows that having Bush line up on the Lions’ offense will force opposing defensive coordinators to pay attention.

“It’s going to force them to bring another man down, more than we had last year,’’ Johnson said on Monday. “You know, if you don’t, Reggie can make you look foolish in the open field.”

When Bush signed with the Lions in March, he said the Lions didn’t need to show him more than one film clip of how defenses line up when they have to keep an eye on Johnson.

After he signed, Bush said: “It’s a running back’s dream. It’s the first thing we talked about when we’re watching film and to see those safeties deep and to see the safeties rolling over, double-coveraging Calvin Johnson, it’s a running back’s dream.

“We have to be able to run the ball in the situation and that’s one of the reasons I wanted to come here to be able to bring a balanced attack and help take some of the pressure off Calvin Johnson and Matthew Stafford and just complement them. I think it’s going to work out well.’’

The two will practice together as OTAs start on Tuesday. They’ll get a better feel for the offense during mandatory minicamp June 11-13.

(Follow @PaulaPasche on Twitter. Order her book,  “100 Things Lions Fans Should Know & Do Before They Die’’ here. It’s also available at bookstores.)