GM Sandy Alderson told ESPNNewYork.com the decision partly was based on Nieuwenhuis being more accustomed to a reserve role, which is what the responsibility currently entails.
David Goldman/Associated PressMatt den Dekker leads the Pacific Coast League with a .331 average.
Den Dekker is hitting .436 (17-for-39) with eight walks and only five strikeouts in his past 10 games with Triple-A Las Vegas. His .331 season average leads the Pacific Coast League.
"It had a little bit to do with the role," Alderson said. "Nieuwy had played as a bench player up here, had platooned in left field. It was probably a more familiar role for him than for Matt. And the fact that [Nieuwenhuis] had been up earlier in the year and had done a pretty good job for us was probably a factor as well."
Asked about den Dekker's performance this season, including a relatively modest 25 strikeouts in 161 at-bats since a June 18 demotion to Triple-A, Alderson said: "Offensively, he's swinging the bat really well. The other thing to take into account is, OK, so what role is he going to play for us, as I just explained with Nieuwenhuis. But obviously we're cognizant of what Matt's doing and we're pleased about it."
Alderson was cagey when asked whether any call-up would wait until September, after rosters have expanded. Still, Alderson seemed to clearly imply that waiting was the likely course of action. Promoting den Dekker sometime in the next 25 days would require dumping Chris Young in all likelihood.
Might there be an opportunity before Sept. 1 for den Dekker?
"There could be," Alderson replied, "but we're not that far from Sept. 1."
Pressed if Abreu was the last subtraction this month, or whether someone like Young might be vulnerable, Alderson added: "We're always evaluating our roster, but as I said, we're getting close to Sept. 1. So it's not a material issue."