Rohan - here is the situation with Marte:
He is the CWS best bullpen P, and management wants to utilize him wherever they think he will be the most usefull in every game. They do not want to pidgeone-hole him into being their 9th inning closer. In most games there will be a situation where a dominate LHP will be the best option out of the bullpen and Marte fills that need - whether it is the 7th, 8th or 9th inning.
Fantasy wise, Marte is very valuable, but not because of his saves. He will be a top 15 P when it comes to helping your overall ERA, and his WHIP will be a big help too. I see 5-10 saves and a handful of wins to go along with those sick %s.
Takatsu is the closer in waiting, but Koch has performed admirably this spring. Unless Koch makes a strong comeback and puts the closer role on lockdown, I see Koch and Takatsu splitting saves while Marte grabs a few here and there. Unless a dominate closer emerges between Koch and Takatsu, I wouldnt draft either before the very last rds. Marte, on the other hand, is a definate mid to late rd pick in standard leagues.