PHILADELPHIA -- Mets lefthander Steven Matz has shown improvement and could pitch Saturday or Sunday, Mets manager Terry Collins said on Thursday.

Matz has been dealing with a stiff back that twice has forced the team to scratch his start. Matz reported improvement after taking medication on Wednesday.

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Though he would appear in relief this weekend against the Nationals, Collins wants Matz to log at least five innings, which is possible with the Mets' starters scheduled to throw abbreviated outings.

Getting Matz in a game will prove critical to his chances of making the postseason roster. Collins wants Matz to pitch in a game because he has only recently returned from two months on the shelf with a partially torn lat muscle.