The move comes as a bit of a surprise given Leino and Helm’s contributions during their stay in Detroit. My guess is that it’s a combination of two factors.
As Malik posits, Tomas Holmstrom must be close to returning. The Red Wings organization has said from the start that they want to see Ericsson before the playoffs and they lose that chance when Homer gets back.
Ericsson’s cap number is higher than that of Leino or Helm. I don’t have the numbers in front of me but it’s probably high enough that he can’t just replace one of them in the lineup, that both need to go with a cheaper alternative brought up to play on a forward line. Downey fits the role of the cheaper player who fits with Ericsson’s cap hit.