Please read the Gospel of Luke, Chapter 22 prior to going any further. This will give you the timing and situation we're in prior to getting to the point.
"Father, if thou be willing, remove this cup from me". Seriously now, did Jesus just ask God to let this cup be removed? Yes, He did, but what exactly was the cup?
Luke 22:44 "And being in an agony he prayed more earnestly: and his sweat was as it were great drops of blood falling down to the ground."
At this point, lets look over a couple of situations that would have rendered the crucifixion of no value.
If Jesus Christ had sinned, even in thought, it would no longer be sinless blood.
If God hadn't been able to raise Jesus Christ from the depths of Paradise or even bringing Him back to life. Had God failed in any part of this, the cross wouldn't have helped us.
Jesus Christ knew a time would come when He'd be nailed to a cross.
Jesus Christ was willing but, what if His body just wasn't strong enough to make it. What if a human health issue became so strong, so intense that Jesus Christ feared His body would shut down prior to getting to the cross.
Hematidrosis, also called blood sweat, is a very rare condition in which a human sweats blood.
Jesus Christ experienced hematidrosis while praying in the garden of Gethsemane before his crucifixion. Granted, not all agree but its the only explanation that fits. Hematidrosis can lead to dehydration, weakness and extremely blood pressure. I believe Jesus Christ feared His body would die prior to getting to the cross, thus the cup being His death prior to finishing His Work on the Cross.
This my opinion, I personally see no other reasonable options.