Take one wet track and add 23 impatient open wheel racing drivers and you're always going to get plenty of incident, as Saturday's first race in the Shell and Pennzoil Grand Prix of Houston doubleheader once again confirmed.

Ganassi's Tony Kanaan had looked set to clinch a podium finish in the race, but as the cars tried to heat up their tyres behind the safety car with one to go on a still-damp track he was spun out by Graham Rahal and left sitting facing the wrong direction - an incident that meant the race would end under yellow and thus guaranteed the win to Dale Coyne Racing's Carlos Huertas.

"Obviously I told Tony I was sorry," Rahal said afterwards. "It was my mistake and I feel bad for Tony. With the stack up on the restart, I was trying to keep the tyres as dry as I could and I was to the left and when it stacked up I just didn't see it at all and I got into the back of him."

Rahal also suffered, losing his own chance at a podium position after being handed a 30-second penalty for causing the accident, which dropped him down to 11th place - but that was little comfort to Kanaan.

"We fought all the way, all day long, and to be taken out like that I think it's stupid," he simmered. "But he was having a good day, too and then ruined his day. I guess I wanted to believe the best. I wanted to believe he didn't do it on purpose. Of course he came and apologized. But that still doesn't take the frustration out of me.

"It's just a shame. Am I mad at him? Yes. Can I turn back time? No. So we have to turn the page and go on to tomorrow."

Another driver to be served a post-race penalty was Kanaan's team mate Ryan Briscoe, who had triggered the final caution by making contact with the rear of Sebastian Saavedra's car in turn 5.

"It was a crazy race," said Saavedra. "I am very sad because the result does not show what an amazing car we had. We were very strong in the wet, making a lot of passes when the conditions were at there worst.

"Unfortunately at the end I got taken out by Ryan Briscoe while looking to have a top-five or better finish," he added. "I'm disappointed, we came from so far back in the field and worked so hard that we deserve a lot better."

The first retirements of the race had been Takuma Sato and Mikhail Aleshin on lap 32, who tangled in turn 6 when the track was still at its wettest. Sato had been running in second place at the time while Aleshin - who had been involved in multiple incidents already by that point - was a lap down. Sata didn't expect Aleshin to put up much of resistance as he went past, but a miscommunication put both men in the wall.

"Aleshin was behind but he was a lap down so I concentrated on Hinchcliffe," explained Sato. "Going into the long sweep on turn five, the only place to overtake was on the inside and that was a wet line too so I stayed on the dry line and he just came in too deep on the outside. We tangled. What he was going to achieve? You can't overtake on the outside on that hairpin."

"I was gaining Takuma from the outside," countered Aleshin. "He closed the inside and I was thinking he was going to leave me some space on the outside, but then he closed the inside and he started to close the outside as well. I had nowhere to go at this point. So unfortunately, there's nothing we could do."

Sato was seen nursing his right hand after the crash, but an evaluation in the in-field care centre confirmed that it was just bruised. "It's sore but we'll be fine for tomorrow," he said.

Mike Conway was also left sightly injured from an accident that left the #20 Ed Carpenter Racing car in the tyre wall at turn 3 a few laps earlier to trigger the first caution of the day.

"The track was drying and we decided to pit and put on the red [option] Firestones slicks," Conway explained. "I wanted to make some time but I locked up the tyres in turn 3. It was still a little wet on the outside, and I got the car into the tire barrier. The right front wing was wrecked and the car stalled.

"The impact bent the steering column a bit and it twisted my left thumb pretty well, too," he added. "It is hurting but nothing serious. It will be sore tomorrow. I just feel badly for the ECR/Fuzzy's team because the way the race finished up. We could have been in the mix at the end. We need to get ready for Sunday's race now."

Former GP2 star Luca Filippi, running for Rahal Letterman Lanigan Racing for the first time this weekend, escaped unhurt after one of the hardest hits of the afternoon when he lost control of the #16 car just before the restart on lap 37 and ended up bounding from one concrete wall to another.

"We never ran on the wet tyres [before the race] so it was a bit tough at the beginning," the Italian admitted. "I think the car was very strong with slicks on and I wanted to try to overtake Simon [Pagenaud at the restart.] I was on the overtake button and wanted to take the last corner as fast as possible and I even anticipated the understeer that was coming from the cold tyres, but I made a misjudgement and I hit the inside wall. It's a shame because everything went well to that point and I think the car was strong in the conditions."

The biggest accident in terms of number of cars involved came on lap 48 when Scott Dixon aquaplaned into the wall in turn 9 and bounced back into the path of his Ganassi team mate Charlie Kimball and Schmidt Peterson Hamilton Motorsport's Simon Pagenaud. It put an end to Dixon's hopes of making up lost ground in the Verizon IndyCar Series championship, also points leader Will Power didn't have the best of days after finishing a lap down in 14th place after spinning into the turn 9 tyre wall on lap 58.

"Hard day today," admitted Power. "If we could have hung in there a little longer we could have been in good shape. I made a mistake there and I feel bad for the Verizon Chevy boys after I went into the wall. That's racing. We'll try it again tomorrow and go for better result."