The Dolphins nailed down some holes on defense with Minkah Fitzpatrick and Jerome Baker. Both players help the Dolphins fill the void/inability to cover running backs and tight ends. The Dolphins lacked the ability to cover from Reshad Jones, TJ McDonald, Kiko Alonso and Lawrence Timmons. They may have corrected those issues with both Minkah Fitzpatrick and Jerome Baker. I added some GIFS so you can see the kind of player he is.

Minkah Fitzpatrick:

Fitzpatrick is one of three players to win both the Jim Thorpe and Chuck Bendarik awards. The other two are Charles Woodson and Patrick Peterson. Fitzpatrick is a leader on and off the field. He is exactly what this defense needs. Not only will he get the players in position, he will make plays.

The play below shows his film preparation. Fitzpatrick calls a blitz at the LOS when he realizes that Tennessee is running an empty set. The sack occurs thanks to Fitzpatrick’s film study.

I can actually see his comparison to Charles Woodson due to his ball skills and ability to be a playmaker. The next three gifs show his ability to take the ball away. The first one is the interception in trail coverage and the second one is him returning that INT for a TD. (103 yard return)

Fitzpatrick was right there to make the pick if his teammate Harrison doesn’t tip the pass.

Fitzpatrick is great covering over the top, covering the tight end, and covering receivers from the slot. Fitzpatrick allows the Dolphins to play matchups and never be out of position. He also gives the Dolphins a ballhawk, something they have lacked for a long time. 
Jerome Baker: 

Baker is an athletic linebacker that is more of a what teams are employing at weak side linebacker in the NFL. At 6’1 228, he plays more like safety that covers well and blitzes well. 
Look how he over pursues here, but stays at home enough to force the QB up the field on the read option. He does a good job of recovering and making the tackle. 
Gesicki is the target here running underneath. Baker does a good job of sitting in his zone and making the tackle behind the LOS. 
He covers Ian Thomas perfectly here. Thomas is lined up as the off TE, running an out and up. Baker cuts off his route and gets the inside leverage to tip the pass. Typically, these routes hurt the Dolphins defense. 
The Dolphins nailed two great picks with Minkah Fitzpatrick and Jerome Baker. Both of them give the Dolphins versatility and the ability to cover tight ends and running backs. Both Fitzpatrick and Baker are guys that can split out and cover receivers from the slot. These guys minimize the mismatches they may face.