United head to Turin for the reverse fixture in the Champions League group game, with Jose Mourinho insisting the match has no real impact on his side.
Lose to Juventus and United will still have an excellent chance of progressing to the knockout stages, if they can beat Young Boys and Valencia in their final group games.
Giggs believes United are improving after a dreadful start to the season, but admitted he cannot understand why the team is so inconsistent.
Ive been really impressed with United in the last four or five games, especially second half, Giggs said.
But I dont know what it is. As a United fan you are scratching your head.
Bournemouth on Saturday were brilliant in the first half, but United were brilliant in the second half. Its just putting that 90 minutes together.
They have proven they can give anyone a game, but if you dont turn up for 45 minutes you will not win.
You have to turn up for 90 minutes and United have the players. They were second best the other week, but I think it will be closer on Wednesday.