There was no need to slide. He was out on a force play at second, but the SS made a motion like he needed to tag Luken. Then Luken tried to slide. The SS should have known it was a force out and Luken does not try to slide. Clearly real bad luck. Luken has been hurt all 3 years here. Sad to think what he could have done.
he wasn't out on a force - that was the problem.
The SS thought that the 1st baseman had stepped on 1st base when he fielded the grounder and thus the force at second was off so he needed to tag Luken - but the 1b had not stepped on the bag although from the SS perspective it was probably hard to tell.
So when the SS caught the ball he was actually not on 2nd base - he had stepped down the line toward Luken in order to tag him since he thought the force was off (incorrectly).
This move to tag Luken confused everyone including Luken - who looked to be like he was just running through the bag and when the SS stepped toward him to tag, he awkwardly tried to start sliding and caught a spike.
The reality is if the SS had just caught the ball on the bag and turned the double play normally - it would not have happened.
Or if Luken had always planned on sliding - which he probably should have been doing regardless of the force being on or not - then it probably wouldn't have happened.