But his big name stars were on the receiving end of a vibrant Leeds attack which should have gobbled up a number of guilt-edged opportunities before Arteta had the chance to get into his players at the break.
The Gunners made Leeds pay for their profligacy with a host of wasted first-half chances before Reiss Nelson scored the victor 10 minutes into the second period.
"I tried to tell them exactly what they've been going to face and after 32 minutes we had gained one duel, I imagine". We changed our attitude, desire and organisation at half-time and then we were completely different. I watched a lot of Leeds games and they battered every team every three days.
"Sometimes it's important to focus on the positive things, but at this stage of our team's development it is more important to play consistently at a good level or better because we have important games coming up", commented Bielsa.
"Thank God, I wasn't happy at all [after the first half]".
"I was thrilled about that and really happy", the Arsenal boss said.
Never mind the players, it is a lesson the men in charge of Leeds's transfer dealings need to heed. They're a unbelievable group and what they've constructed is very efficient.
Arteta said: 'They are a nightmare for every team to play.
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"We should have achieved to try and play a match more balanced".
After the match, manager Mikel Arteta expressed his content with how his side bounced back from an terrible first 45 minutes to book their place in the next round of the competition.
"The first half of the group was very, very optimistic for us".
"In the second half the control of the match changed a lot".
"Inside the first half we pressed the opponents' defence additional and have been able to assault fast".