James Anderson has warned New Zealand to expect more aggressive bowling on the second day of the second Test at Old Trafford.
The Lancashire seamer was speaking after putting Daniel Flynn out of action with a bouncer which knocked out one of the Kiwi batsman's teeth.
Anderson later struck Jacob Oram on the helmet in a fiery afternoon session as the tourists reached 202-4 before bad light stopped play.
"I went up to him as soon as I hit him and asked him whether he was all right but I didn't get a reply," said Anderson of the ball which left Flynn bleeding heavily from the mouth.
"It is just one of those things, I am trying to get him out and I want to make it as uncomfortable for him as possible.
"It is just one of those things that happen, people do get hit.
"There was blood everywhere as soon as it hit him so we knew he needed a bit of help.
"When you hit someone in the head it generally encourages bowlers to do it again because certainly with Oram we thought it was a bit of a weakness.
"He didn't look that comfortable and so you're just going to keep doing it when someone plays it like that.
"We do look at the bouncer as a real attacking option, especially against the Kiwis.
"I thought I had a pretty good rhythm as well, so I thought I would carry on."
Anderson struggled in his initial spell of 4-0-23-0 and it took a switch of ends in the afternoon to gee things up, after left-armer Sidebottom halted the 80-run stand for the first wicket and claimed another in his next over.
"We clawed it back well in the last half hour before lunch and we came out really strong and aggressive after lunch," Anderson said.
"The Stretford end is my preferred end when I play here but the wind was a bit tricky today.
"It is usually at my back from the Stretford end but it was a bit different today and it was a nice to have run from the other end.
"The wind was behind me, I could run in a bit more easily and when you're trying to be a bit more aggressive and bowl bouncers you can use that to your advantage."
Opener Jamie How, who made 64 before nicking a ball from Anderson through to Tim Ambrose, said Flynn would be fine after undergoing treatment.
"He's undergone a bit of dentist work but he's a tough little fella and he'll be all right," How said.
"It is never nice seeing a team-mate like that and any hit in the helmet causes concern."
Having shared in New Zealand's biggest opening alliance since Mark Richardson and Stephen Fleming broke three figures against England on the 2004 tour here, he added: "It was nice because when you win the toss and bat it's important to get a good start."