Chelsea hosted the Gunners at Stamford Bridge on Tuesday in a game that saw the Blues going against an Arsenal squad with only 10 players on the pitch during the second half. The match ended in a draw, 2-2, and team manager Frank Lampard acknowledged they could have won if not partly for Mesut Ozil.

Lampard said Chelsea failed to take control of the game in its entire duration. It seemed to be the case in the first half as the club boss admitted that in the first 15 minutes, he was quite happy with how the Blues were playing.

Then the Ozil factor appeared to have kicked in afterward, and his side suddenly developed problems.

"Ozil pulling out to the side and giving you some problems and I think we ended up being in a kind of middle ground," Metro reported the Chelsea boss as saying.

It was a puzzle though that the German playmaker disturbed the plan laid out by Lampard as Ozil was pulled out by Arsenal coach Mikel Arteta with his team trailing at 0-1. Then a little later, the Gunners continued on and with only 10 members as Arteta decided against sending in a replacement he subbed.

It was a chance for the Blues to go aggressive and score a win, but that did not happen. Lampard said it did not sink in on his players' mindset that they are of the advantage, that it was a full squad against a team lacking one man on the pitch.

"Well I think probably for 15 minutes in the first half it did because I think we were still probably in the mindset of them with 11," Lampard explained, and making clear there was no excuse for the lapse.

He added he was disappointed that his side failed to seize the opportunity, and the level of aggressiveness displayed, notably for a home match, was not enough. It was frustrating that Chelsea played at Stamford and faced a 10-man squad, but all the advantages handed to the club failed to produce the expected result, the team manager said.

He conceded Chelsea blew the chance of picking the points and make a happy crowd at Stamford.

"The initiative is on us to be really ruthless about doing the right things, to move the ball quick enough, to take your chances when they came along. I thought we moved it quick enough at times but we didn't take our chances when we got them," the Daily Star reported Lampard as saying.

On that particular game against Arsenal, Lampard thought Chelsea lacked the killer instinct.

"Being tentative when they've got 10 is wrong, you have to go in and still be really positive to make sure they don't get out. And they had a few moments and they fought for it and that's what they should do in a London derby," said the Blues head coach.