INDIANAPOLIS — Wednesday’s open practice at Lucas Oil Stadium stirred some primal feelings in Indianapolis Colts linebacker Robert Mathis.

“As soon as you stepped on the field, you got that little jolt up your spine like you’re ready to hit somebody,” the 10th-year veteran said.

“Like for real. But it will come when it comes, and we’ll just wait to get everything done in the meantime.”

Mathis resisted the urge to light up any of his teammates, though he and his fellow defenders did manage to have little fun with rookie quarterback

Andrew Luck.

As the offense came to the line of scrimmage to start a two-minute drill, Mathis began dancing at his spot in the flat and repeatedly shouted

“Andrew” while the rest of the Colts defense responded with “Luck.”

Antics such as those and an estimated crowd of 7,500 welcomed Luck during his first activity in his new home.

“It was great to see all of the fans out here,” the No. 1 overall pick out of Stanford said. “It was definitely the most fans that I have ever practiced in front of. So it was fun to feel the support, and we got better.”

Colts fans have suffered through a tumultuous offseason following a disastrous 2-14 campaign in 2011. Some fans showed up wearing Denver Broncos gear Wednesday, throwing their support behind former Indianapolis quarterback Peyton Manning and his new team.

One industrious young man wore a jersey that was orange on the front with the No. 18 and blue on the back with Luck’s last name and his No. 12.

The switch from Manning to Luck, and the fans’ reaction to it, will be an unfolding story throughout the 2012 season. But first-year head coach

Chuck Pagano believes his team put a good first step forward in front of the home crowd.

“I know what they went through last year,” Pagano said. “In talking with the players that we’ve got currently on the team that were here last year, (the fans) were out here no matter what. As bad as things were, they were here. I really want to thank the fans for coming out today.”

Pagano said it will be crucial for the Colts to rebuild a strong homefield advantage. He pointed out a team can always make the playoffs by winning all eight of its home games and splitting its eight road contests.

Luck echoed those feelings and said he’s “looking forward to playing in front of the best football crowd in America.”

He got off to a rough start in front of part of that crowd Wednesday.

During individual work, something was missing on the timing between Luck and his receivers. He overthrew a couple of passes down the sideline and threw a few more a step behind his target on crossing patterns across the field.

Pagano took the blame for Luck’s early struggles, saying they were caused in part by a practice schedule that had special teams work slated after

warmups and before the players began their individual drills.

“I think it is on me more than anything else, with the way we set the thing up,” Pagano said. “That is why he started a little bit slow. So once he got going, you could see he got into a rhythm and got the offense moving and generating some yards.”

Indeed, Luck rebounded impressively.

In 11-on-11 and 7-on-7 drills combined, he completed 26 of 37 passes. That total includes three spikes to kill the clock during two-minute drills, meaning Luck threw just eight incompletions against defenders Wednesday.

In eight practices with the Colts, Luck has yet to throw an interception.

He looked particularly sharp Wednesday on a lightning-quick throw over the middle that sprinted past a diving linebacker and hit wide receiver Jeremy Ross in stride for a big gain.

Luck also showed nice touch on a two-yard fade pass to Austin Collie for his first touchdown at Lucas Oil Stadium.

Collie made a late adjustment on the ball in the end zone and caught it as he fell to the ground, and Luck said he learns a lot from every rep he gets with his new teammates.

“Just to get out here and throw and see how he makes an adjustment is huge,” Luck said of the touchdown pass. “I think it helped that it wasn’t

Day 1 for us, but that is something that we will have to continue to work on, though.”

Luck’s delivery can be a bit deceiving. In baseball, pitchers with motions similar to Luck’s are said to throw “easy heat.”

It doesn’t look as though they are expending much effort on the mound, but the ball is moving more than fast enough when it reaches the batter.

According to veteran Reggie Wayne, Luck’s passes have much the same effect.

“I think you (media) guys are going to get on him about the way he throws the ball,” Wayne said. “It looks kind of nonchalant, effortless. But he throws a pretty doggone good ball. He has a nice spiral to it, has some zip and he puts it in the right spot. So once we get all our timing down, and we’ll be able to do all that stuff before training camp and throughout training camp, I think we’re going to do some special things.”