This is a tough question.

For the Dodgers I pick Yasiel Puig.  He never did live to expectiations after a first great month in the majors.

For the Rams I pick Sam Bradford.  Injuries shortened his career.  The Rams did reveive a 2 second round pick for him when they traded him to the Eagles.  The Rams used the pick as part of the haul they used to acquire Jared Goff.

For the Kings I will go with Alexander Frolov.  He did have to 30 goal seasons for them, but he only played 6 years for them.

Marcus Mariota of the Tennessss Titans

Johnny Bright

1952  5th pick of the 1st Round  He choose to play in CFL then in Philadelphia which was a racist city at the time.  Even during WWII troops had to be sent to Phila to protect Trolley car conductors and motormen as African-American were given those jobs instead of cleaning them.   He became a CFL Hall of Famer 

Bud Grant

The Eagles 1950 first round draft pick chose to play in NBA for Lakers.  He then played 1951 &1952 for the Eagles before in a dispute over money he headed to Winnipeg to play and coach. In 1967 he would become coach of NFL Minn Vikings.  He became a Hall of Famer in both  CFL and NFL

Eric Davis, Mr Clutch for the Reds for a while, partying with Strawberry rumored to be his downfall.

The 2000 NBA draft class. Produced one of my favorite players in Kenyon Martin, but as a whole accomplished very little. 

I have far more thoughts of players who were traded and shouldn't have been, which destroyed a team's hopes for success...Kenyon is on that list too actually. 

Looking for a specific name, I heard all kinds of good things about Rod Grizzard, heard he was the next big thing etc...he didn't make the Wizards out of training camp and never played in the NBA. 

This is an interesting on. For me, a modern example would be Rusney Castillo.

What I find intriguing are some of the names mentioned. I'm thinking the OP was looking for true flameouts. Sometimes we dont know what to expect out of a player and they could be playing to their capabilities, it just isn't what we were hoping for. Puig for example. All things considered he's had a decent career and is playing to exactly his level. The way he started he looked like he was heading for bigger things. Coming from Cuba with all the hype didn't help. Fred Lynn is a comparable. He burst onto the scene and he was the next coming of Williams and Yaz. Didn't work out that way as he settled into the player he was as time moved on, his true capability.

Too many Oilers, not enough energy!! LOL

Pretty much 80% of our first round picks I would use, our luck has been low at best. Most current ones I can think of, Nail Yakupov, Jesse Puljarvi, Linus Omark, one plays in Ottawa now (well use to) and like I said several others.

On this, I have to go with what my father always said. Just because they are the best at the time in the minors or in college, does not mean they will have the chops to keep up with the pros. You earn that star quality playing in the pros, you don't walk in with it.

We see it as one step up to get into a pro team. But the gameplay is really 1000 steps up. Compared to what they were doing. 

The hype is just words their manager uses to get them more money so they can get a bigger cut.

All these things are true If they were not. Then there would be no names on this post. But it's to easy to come up with a few names. It's the problem of just to much hype with no pro experience.

That should be the title of this post "Who had to much hype with no pro experience." Shoulda Woulda Coulda, is beliving the hype was true and you just can't do that in real life.

I wouldn't be surprised if your failed prospect (Puljujarvi) gets traded for ours before next season (Lias Andersson). 

Is that what the rumor mill has going on over in NY, over here we just make fun of him. Big baby cant hang with the big boys. I think his career will disappear in Europe somewhere. If anything Id think we would want picks for him instead of more dead wood lol.