It seems silly to call someone like Yulieski Gurriel a "prospect" or even a rookie: the Houston Astros third baseman made his MLB debut yesterday but is 32 years old and a long-established star in Cuba. When the Astros signed him as a free agent last month, I wrote the following:
the Houston Astros signed Cuban infielder Yulieski Gurriel to a five-year contract worth a reported $47,500,000. At age 32 Gurriel is not subject to international bonus pool restrictions and should be viewed like a veteran free agent signing, not a prospect. He has a long track record in Cuba and was one of the brightest stars in Serie Nacional from the age of 18. He also played 62 games in Japan in 2014, hitting .305/.349/.536 for Yokohama.
Although he's on the downside of his career at age 32, Gurriel is a potent hitter who should provide above-average power with a superior contact hitting approach: he fanned just three times while drawing 38 walks in 174 plate appearances in Cuba in 2015. He's also a very good defensive third baseman. He hasn't played competitively in 2016 and may need some time to gear up, but we'll certainly see him in the majors later in the season. It remains to be seen what impact this will have on other players in the Astros system like Alex Bregman.
The Astros moved Gurriel very quickly, giving him two games in the Gulf Coast Rookie League, four in the High-A California League, five in the Double-A Texas League, and four more in the Triple-A Pacific Coast League. All the jumping around, a 15-game composite sample size, and the need to work off his rust makes the numbers rather meaningless when it comes to projecting the future, but for what it's worth he slashed .250/.262/.429 with four doubles, two homers, 14 RBI, two walks, and 15 strikeouts.
The whiff rate is high and he hasn't shown the expected contact hitting/plate discipline approach, but given the circumstances I wouldn't make a big deal out of that yet. Certainly the isolated power has been there and he impressed the Astros enough for them to advance him rapidly. He went 1-for-2 with a walk in his MLB debut and Houston's professional scouting director Kevin Goldstein noted the following on his Facebook page
Yuliesky Gurriel centered a 3-1 fastball up the middle on a single that came off the bat at more than 100 mph. There weren't a lot of fans there to see it, and there wasn't a ton of fanfare, but it was a big deal and in my mind an important marker in Cuban baseball and it's difficult-to-define relationship with MLB. It also made me as happy as the win did.
Getting Gurriel fully acclimated to the majors and United States culture in general should be the goal the rest of the season. Keep that in mind if he has some rough patches. My guess is that he lives up to expectations and emerges as a significant offensive force in 2017.