Mantha will attend boxes classes this summer to "toughen his general approach to the game," The Detroit News reports.
Larkin will play for Team USA in the 2018 World Championship in Denmark next month, Ansar Khan of MLive.com reports.
Nielsen will represent his native Denmark at the 2018 World Championship, Ansar Khan of MLive.com reports.
Jensen finished with 15 assists as his entire point total through 81 games this season.
Ouellet failed to score but put up seven assists through 45 games this season.
Kronwall appeared in 79 games this season, notching four goals, 23 assists (15 power-play points) to complement 82 hits and 107 blocked shots.
Daley wound up with nine goals, seven assists, and a minus-5 rating through 77 games in his debut season with Detroit.
Witkowski provided a mere four points through 31 games in 2017-18, as he was a part-time player who only averaged 6:53 of ice time.
Frk's rookie campaign amounted to 25 points (11 goals, 14 assists) through 68 games. He also factored into nine man-advantage scoring plays.
Nielsen's final output for the 2017-18 campaign consisted of 16 goals and 17 assists through 79 games.
Larkin led his team with 63 points (16 goals, 47 assists) in the 2017-18 campaign.
Hicketts was bumped back down to AHL Grand Rapids on Wednesday.
Ehn was assigned to AHL Grand Rapids from Frolunda of the Swedish Hockey League on Tuesday, Ansar Khan of MLive.com reports.
Jensen has picked up the offensive pace with two assists over the last three games.
Larkin scored his 14th goal of the season in Saturday's 2-0 win over the Senators.
Howard made 29 saves on 32 shots in a 6-3 win over the Sabres on Thursday.
Nielsen picked up two helpers in a 6-3 win over the Sabres on Thursday.
Mantha scored a goal and had an assist in a 6-3 win over the Sabres on Thursday.
Howard will patrol the crease against the Sabres in Buffalo on Thursday, NHL.com reports.
DeKeyser has two assists, five hits and 10 blocked shots over the last three games.
Frk was the primary distributor on Frans Nielsen's power-play goal in Tuesday's 5-2 home win over the Penguins.
Mantha only has two points (assists) since wreaking havoc on the Bruins with a four-point showing March 6.
Nielsen converted a power-play chance in Tuesday's 5-2 home win over the Penguins.
Larkin's pair of assists in Tuesday's 5-2 home win over the Penguins widened his career-best point total to 56 through 77 games.
Howard staved off 22 of 24 shots from the Penguins on Tuesday, as he cruised to a 5-2 home win.