Approaching the end of May, and the unofficial start of summer with Memorial Day weekend, here are our five must-adds off your fantasy baseball waiver wire for the coming week.

Note: All stats are through May 19.

5. Austin Riley, 3B/OF, Atlanta Braves

Riley had a power surge at Triple-A early this month (1.406 OPS, 12 home runs, 27 RBI) and made his debut for the Braves last Wednesday night. He proceeded to hit a home run in his second big league at-bat, then added as second dinger last Friday night.

Over five games, with a hit in each of his first four games, Riley is hitting .421/.421/.789 (8-for-19) with two home runs and five RBI.

Riley is a third baseman by trade, but he has played four games in left field for the Braves and is on track to add outfield eligibility in fantasy leagues. The only thing keeping him from a higher place on his list is a high ownership rate in Yahoo! league

Yahoo! Ownership: 66%
ESPN Ownership: 44.2%

4. Craig Kimbrel, RP, Free Agent

Once the draft is in the books in early June, and the pick compensation attached to him goes away, Kimbrel should be signing somewhere. The Tampa Bay Rays, Minnesota Twins and Atlanta Braves seem like three strong possibilities, as well as the Milwaukee Brewers.

It may take him some time to ramp up, as he possibly goes on some sort of minor league excursion and pitches some lower leverage innings, but Kimbrel should be getting save opportunities fairly quickly. He showed some cracks in terms of control last year, but pitching for a contending team lines him up to make a fantasy impact.

Kimbrel is obviously purely a speculative add-and-stash right now. But if you have the ability to use a roster spot in that way, feel free to swap out an underachieving or injured player for the prospect of substantial future value.

Yahoo! Ownership: 74%
ESPN Ownership: 64.1%

3. Keston Hiura, 2B, Milwaukee Brewers

After hitting .333 with 11 home runs to start the season at Triple-A, Hiura made his major league debut last Tuesday night. He hit his first major league home run on Sunday, and he has three multi-hit games over his first six.

Hiura hit .293 with 13 home runs, 43 RBI, 74 runs scored and 15 steals between High-A and Double-A last year. So he would project to be a four-category contributor, even with some expected ups and downs.

A good Brewers lineup will raise Hiura up, even if he continues hitting sixth or seventh as he has. At a shallow fantasy position, Hiura should be owned in all mixed leagues.

Yahoo! Ownership: 47%
ESPN Ownership: 22.8%

2. Brendan Rodgers, SS/2B, Colorado Rockies

With Garrett Hampson and Ryan McMahon struggling, and Hampson sent down, Rodgers pushed down the door to the big leagues with a great start at Triple-A (.356, 9 home runs, 10 doubles, 21 RBI). In his first two games for the Rockies, he has one hit in eight at-bats with an RBI and four strikeouts.

Rodger is eligible at shortstop immediately in fantasy leagues, but he’s in line to take the second base job for Colorado and leave everyone else behind. Both of his games have been at second base thus far, so eligibility at that spot is coming.

A hitter-friendly environment helps Rodgers, as does a solid lineup around him. Expect some ups and downs, as shown early, but the former first-round pick is at worst a good middle infield stash in mixed leagues.

Yahoo! Ownership: 39%
ESPN Ownership: 19.7%

1. Ty Buttrey, RP, Los Angeles Angels

Buttrey picked up his second save of the season on Sunday, as he went 1.2 innings as well. He now has a 0.76 ERA with 31 strikeouts and just four walks over 23.2 innings (21 appearances) this season.

Buttrey is not strictly locked into the closer role right now, with Hansel Robles and Cody Allen lingering in the mix for saves too. But he’s been the Angels’ best reliever, and even with a split of saves his other stats (see the strikeouts and nine holds so far this season) carry substantial value.

Buttrey is operating off the fantasy radar right now. But all that means is there’s an opportunity to get him without the other owners in your league noticing, then reap significant rewards down the road.

Yahoo! Ownership: 26%
ESPN Ownership: 8.7%