I think it's clear the Indians will add a reliever or two, and there will be no shortage of potential options.
Raisel Iglesias - There's been no indication that the Reds want to deal him, but if you're the Reds, why wouldn't you? Iglesias is 28, signed through 2020, and is low-cost, owed $4.5 M this year and $5 M each of the next two seasons. Iglesias/Miller/Allen would be downright scary, and he'd soften the blow if both Allen/Miller leave this winter.
Brad Hand - Hand is only 28 and locked in through 2021. He's an elite LH reliever who, like Iglesias, would help both short and long term.
Zach Britton - In the final year of his deal and almost certain to be traded. He's expected back by June, so he'll have an opportunity to prove he's healthy. If he is, he's one of the best in the game.
Brad Brach - Also a free agent at the end of the season, Brach is one of the most underrated relievers in the game.
Kelvin Herrera - Another soon-to-be free agent, Herrera has been absolutely dominant early on.
Joakim Soria - He isn't elite anymore, but he's a solid relief arm that probably won't cost much in July. Free agent this winter.
Nate Jones - Jones is a fantastic reliever that has never been able to stay healthy. A free agent this winter on a non-contender, he likely wouldn't cost a ton.
Other Possibilities: Jim Johnson, Peter Moylan, A.J. Ramos, Brad Ziegler, Jerry Blevins